Investments in fixed maturity securities (Tables)

6 Months Ended

Jun. 30, 2018

Investments, Debt and Equity Securities [Abstract]

Schedule of investments in securities with fixed maturities

Investments in securities with fixed maturities as of June 30, 2018 and December 31, 2017 are summarized by type below (in millions).

	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
June 30, 2018
U.S. Treasury, U.S. government corporations and agencies	$	3,463	$	10	$	(35)	$	3,438
U.S. states, municipalities and political subdivisions		452		17		(5)		464
Foreign governments		7,551		56		(42)		7,565
Corporate bonds		5,968		453		(8)		6,413
Mortgage-backed securities		585		62		(3)		644
	$	18,019	$	598	$	(93)	$	18,524
December 31, 2017
U.S. Treasury, U.S. government corporations and agencies	$	3,975	$	4	$	(26)	$	3,953
U.S. 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 fixed maturity securities at June 30, 2018 are summarized below by contractual maturity dates. Amounts are in millions. Actual maturities may differ from contractual maturities due to early call or prepayment rights held by issuers.

	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	$	6,863	$	9,439	$	399	$	733	$	585	$	18,019
Fair value		6,876		9,507		448		1,049		644		18,524