Berkshire Hathaway (NYSE:BRK-A)(NYSE:BRK-B) shareholders should be pleased with the company's earnings report for the second quarter. The Omaha-based conglomerate reported operating earnings of $6.9 billion, a 67% increase over the year-ago period, due primarily to higher profits in insurance and a lower tax rate thanks to last year's corporate tax cut.

Here's how Berkshire's quarter stacked up, segment by segment.

Insurance -- $2.1 billion profit

Berkshire's insurance companies had a stellar second quarter. The company reported that its insurers earned $943 million from underwriting, far better than a $22 million loss in the year-ago period. Investment income earned from interest and dividends from the float jumped to $1.14 billion, up from $965 million last year.

Notably, all of Berkshire's insurance units generated an underwriting profit in the second quarter. A breakdown of pre-tax underwriting profits by insurance segment appears below:

Insurance segment Q2 2018 Q2 2017 GEICO $673 million $119 million BH Reinsurance $297 million ($375 million) BH Primary Group $234 million $232 million Total underwriting $1,204 million ($24 million)

GEICO's quarter could be described as simply exceptional. The company benefited from an 8.7% increase in prices over the last 12 months, as well as a 4.9% increase in the number of policies in force during the period. During the second quarter, GEICO posted a combined ratio of 91.9%, an improvement from its combined ratio of 97.9% last year.

Speaking broadly, 2018 has been largely devoid of large catastrophe losses so far, a reprieve from last year, when natural disasters in the form of hurricanes and earthquakes took their toll on Berkshire's underwriting results.

Railroad -- $1.3 billion profit

We knew beforehand that BNSF was likely to benefit from higher railcar volumes, as its carloads report showed a healthy 4.9% increase in the number of cars that moved over its rails in the second quarter.

On an after-tax basis, BNSF's profit increased by about 37% compared to the year-ago period. Pre-tax profit increased by about 8%, however, as a reduction in corporate tax rates, not increased volume or pricing, had the largest effect on profit growth. (Its tax rate declined from 37.7% in the year-ago period to 20.9% in the most recent quarter.)

BNSF is in many ways a bet on the U.S. economy and commodity prices. In its quarterly filing, Berkshire said that shipments of industrial product volumes increased by 10.4% in the second quarter, driven by demand for sand, petroleum products, steel, and plastics.

Manufacturing, service, and retailing -- $2.1 billion profit

This segment essentially includes every Berkshire subsidiary that isn't broken out on its own, but it's fair to think of it as being primarily driven by Berkshire's manufacturing concerns, which produce the vast majority (about 74%) of the segment's profit. Operating earnings increased by roughly 29% from the year-ago period.

Berkshire's major manufacturers reported impressive revenue growth in the second quarter. In its filings, Berkshire said that Precision Castparts saw its revenue grow 6.5% in the second quarter over the year-ago period, though pre-tax profit fell by 8.9%, due to costs associated with plant shutdowns and outages, and new aircraft programs that have high up-front costs, despite the expectation they will generate larger profits in future accounting periods.

Lubrizol revenue increased 9.5%, due to higher prices, improved product mix, and favorable currency fluctuations. IMC and Marmon reported revenue increases of 21.4% and 10.2%, respectively, compared to the same period a year ago. The aforementioned companies make up the bulk of Berkshire's "industrial" manufacturers, which produce the highest margins of any of its manufacturing, service, and retail businesses, and about half of overall profits in the segment.

Utilities and energy -- $581 million profit

The utilities and energy businesses are almost annuity-like, since they generate the bulk of their earnings from the sale and distribution of power in regulated markets across the United States. Operating earnings for this segment increased 14% year over year.

After backing out the real estate brokerage business, Berkshire's utilities reported revenue growth of 3.6% year over year, driven by acquisitions and new projects, partially offset by rate decreases in regulated markets where the companies have to pass on the benefit of a lower tax rate to customers. (PacifiCorp revenue, for example, declined by about $58 million year over year, of which $53 million was driven by lower rates as a result of tax reform.)

Finance and financial products -- $429 million profit

Clayton Homes, which sells manufactured and site-built homes, is the star of this segment. Revenue for the homebuilder increased by 26% to $1.5 billion, as the company benefits from increased home sales volume and rising finance profits.

The outsize increase in revenue is partially driven by the sale of site-built homes, where land is included in the sales price (manufactured home sales do not have attached land value). Clayton Homes' pre-tax earnings increased 19% over the year-ago period, substantially lower than the 26% increase in revenue.

Other events and important details

There's more to an earnings report than just the dollars and cents of what a business earned in a recent 13-week period. Here are a few things that are worth keeping an eye on:

Cash holdings -- Berkshire ended the quarter with about $111 billion in cash. With so much cash on hand, it's safe to say that Buffett's "elephant gun" is still loaded for a large acquisition. Net of the $20 billion of cash Buffett likes to have around as a rainy day fund, Berkshire has roughly $91 billion of "excess" cash.

Stock concentration -- Berkshire may own a lot of stocks, but a handful are particularly important to its financial results quarter to quarter. Note that about 70% of its stock portfolio is attributed to just five companies -- Apple , Wells Fargo , Bank of America , Coca-Cola , and American Express . To put that in perspective, the five largest companies in the S&P 500 make up less than 16% of the index's value.

, , , , and . To put that in perspective, the five largest companies in the make up less than 16% of the index's value. Share repurchases -- Now that the quarterly report is filed, Berkshire can start repurchasing stock whenever Buffett and Charlie Munger deem it an attractive investment. In July, Berkshire changed its buyback policy, removing a self-enforced rule to only repurchase shares at a valuation of 1.2 times book value. Shares recently traded at about 1.4 times book value.

All in all, Berkshire's second quarter shows just how much it can earn when everything goes its way. Its insurance companies were the star performers this quarter, producing robust underwriting profits nearly $1 billion greater than they earned in the year-ago period.