Investments in fixed maturity securities (Tables)

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Schedule of investments in securities with fixed maturities

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

	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
December 31, 2018
U.S. Treasury, U.S. government corporations and agencies	$	4,223	$	22	$	(22)	$	4,223
States, municipalities and political subdivisions		182		7		—		189
Foreign governments		7,480		50		(28)		7,502
Corporate bonds		7,055		408		(23)		7,440
Mortgage-backed securities		487		59		(2)		544
	$	19,427	$	546	$	(75)	$	19,898
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 fixed maturity securities at December 31, 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		$  6,973	$	10,937	$	438	$	592	$	487	$	19,427
Fair value		6,982		10,994		494		884		544		19,898