Apple, Microsoft and Google are the top three cash-rich U.S. companies across all sectors of business, not including banks and other financial institutions — holding a combined $391 billion in cash as of the end of 2015, or more than 23 percent of the entire $1.68 trillion held by the nation’s non-financial corporations.

Apple leads the pack with $215.7 billion in cash, followed by Microsoft at $102.6 billion, and Google at $73.1 billion.

The numbers are documented in a new report from Moody’s Investors Service that shows an unprecedented concentration of cash in the tech sector. For the first time, the top five companies on the Moody’s cash ranking are tech companies, with Cisco and Oracle following Apple, Microsoft and Google. Technology companies overall held $777 billion in cash, or 46 percent of the total cash across all non-financial industries.

That was despite the fact that tech companies led all sectors with $118 billion in share repurchases in 2015, while also spending heavily on acquisitions and capital expenditures.

“Despite stronger returns of capital to shareholders, we expect the technology sector cash concentration will grind higher over the next year because of the sector’s strong cash flow generation,” writes Moody’s in the report. “The technology sector generated 63% of the total rated non-financial free cash flow in 2015, up from 37% in 2007. Excluding the energy sector, tech comprised 40% of non-financial free cash flow in 2015, similar to the 42% average since 2007.”

Further down on the list, Amazon and Facebook came in at #17 and #18 on the Moody’s ranking, respectively, with $19.8 billion and $18.4 billion in cash.

A large portion of tech company cash is held overseas, highlighting ongoing roadblocks corporate tax reform that would help companies repatriate those funds. Moody’s estimates that Apple, Microsoft, Cisco, Google and Oracle have $441 billion overseas, representing 87 percent of their cash.