(3)	Investments in fixed maturity securities

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

Investments in foreign governments include securities issued by national and provincial government entities as well as instruments that are unconditionally guaranteed by such entities. As of December 31, 2018, approximately 88% of our foreign government holdings were rated AA or higher by at least one of the major rating agencies.

 

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