(Reuters) - MetLife Inc MET.N reported a 13.8 percent fall in quarterly operating income on Wednesday, hurt by a charge related to the spin off of its U.S. retail business, Brighthouse Financial, and the insurer authorized a $2 billion share buyback plan.

A MetLife Inc building is shown in Irvine, California, U.S., January 24, 2017. REUTERS/Mike Blake

MetLife said that it intends to divest its remaining Brighthouse Financial Inc BHF.O common stock through an exchange offer for MetLife common stock during 2018.

The quarter included the results of Brighthouse's final month with MetLife before the spinoff became effective on Aug. 4, following which MetLife ceded the title of the largest U.S. life insurer by assets to Prudential Financial PRU.N.

New York-based MetLife booked a third-quarter charge of $1.1 billion related to the Brighthouse spinoff, less than the $1.4 billion it had previously estimated.

The third quarter is the first indication of how MetLife may perform without Brighthouse, whose assets include variable annuities, which led to swings in MetLife’s overall performance.

“A lot of that volatility went out the door with Brighthouse,” Wells Fargo Securities analyst Sean Dargan said before the company released its results.

Net operating income, which excludes investment and derivative gains or losses, fell to $1.17 billion, or $1.09 per share, in the quarter ended Sept. 30, from $1.36 billion, or $1.22 per share, a year earlier. [nBw3r2vF1a]

Analysts on an average were expecting a quarterly profit of 90 cents per share, according to Thomson Reuters I/B/E/S. It was not immediately clear if the numbers were comparable.

MetLife’s operating costs increased 4.6 percent to $14.99 billion.

Variable investment income dropped nearly 20 percent to $236 million due to the sale of a real estate joint venture interest in the prior year period and lower prepayment fee income, the insurer said.

(This version of the story corrects previous estimate of Brighthouse spinoff costs to $1.4 billion, not $1 billion; and that $1.1 billion charge is less, not more, than estimated)