Investments in fixed maturity securities (Tables)

3 Months Ended

Mar. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Schedule of investments in securities with fixed maturities

Investments in securities with fixed maturities as of March 31, 2018 and December 31, 2017 are summarized by type below (in millions).

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
March 31, 2018
U.S. Treasury, U.S. government corporations and agencies	$	3,633	$	11	$	(36	)	$	3,608
States, municipalities and political subdivisions		737		30		(8	)		759
Foreign governments		7,837		83		(32	)		7,888
Corporate bonds		6,308		519		(8	)		6,819
Mortgage-backed securities		761		88		(3	)		846
	$	19,276	$	731	$	(87	)	$	19,920
December 31, 2017
U.S. Treasury, U.S. government corporations and agencies	$	3,975	$	4	$	(26	)	$	3,953
States, municipalities and political subdivisions		847		19		(12	)		854
Foreign governments		8,572		274		(24	)		8,822
Corporate bonds		6,279		588		(5	)		6,862
Mortgage-backed securities		772		92		(2	)		862
	$	20,445	$	977	$	(69	)	$	21,353

Schedule of amortized cost and estimated fair value of securities with fixed maturities

The amortized cost and estimated fair value of securities with fixed maturities at March 31, 2018 are summarized below by contractual maturity dates. Actual maturities may differ from contractual maturities due to early call or prepayment rights held by issuers. Amounts are in millions.

	Due in one year or less		Due after one  year through five years		Due after five  years through ten years		Due after  ten years		Mortgage- backed securities		Total
Amortized cost	$	7,178	$	9,884	$	460	$	993	$	761	$	19,276
Fair value		7,227		9,982		515		1,350		846		19,920