Investments in fixed maturity securities (Tables)

9 Months Ended

Sep. 30, 2018

Investments, Debt and Equity Securities [Abstract]

Schedule of investments in securities with fixed maturities

Our investments in fixed maturity securities as of September 30, 2018 and December 31, 2017 are summarized by type below (in millions).

	Amortized   Cost		Unrealized Gains		Unrealized Losses		Fair     Value
September 30, 2018
U.S. Treasury, U.S. government corporations and agencies	$	3,626	$	8	$	(35)	$	3,599
U.S. states, municipalities and political subdivisions		276		15		(1)		290
Foreign governments		7,362		45		(37)		7,370
Corporate bonds		6,029		436		(7)		6,458
Mortgage-backed securities		502		56		(4)		554
	$	17,795	$	560	$	(84)	$	18,271
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 September 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	$	7,275	$	9,057	$	387	$	574	$	502	$	17,795
Fair value		7,274		9,108		435		900		554		18,271