Variable Interest Entities (Changes in Level 3 Assets and Liabilities) (Details 2) - Consolidated investment entities [Member] - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Transfers from Level 1 to Level 2, assets		$ 0	$ 0
Transfers from Level 2 to Level 1, assets		0	0
Transfers from Level 1 to Level 2, liabilities		0	0
Transfers from Level 2 to Level 1, liabilities		0	0
Corporate debt securities [Member]
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Balance, at the beginning of the period			0
Transfers into Level 3			2
Balance, at the end of the period			2
Common stocks [Member]
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Balance, at the beginning of the period		4	5
Total gains (losses) included in net income	[1]	4
Transfers into Level 3		4	1
Transfers out of Level 3		(1)	(2)
Balance, at the end of the period		11	4
Changes in unrealized gains (losses) included in income relating to assets held at end of period	[1]	4
Syndicated loans [Member]
Summary of changes in Level 3 assets measured at fair value on a recurring basis [Rollforward]
Balance, at the beginning of the period		180	254
Total gains (losses) included in net income	[1]	2	3
Purchases		18	55
Sales		(1)	(8)
Settlements		(11)	(23)
Transfers into Level 3		61	72
Transfers out of Level 3		(49)	(130)
Balance, at the end of the period		200	223
Changes in unrealized gains (losses) included in income relating to assets held at end of period	[1]	$ 2	$ 2

[1] Included in net investment income in the Consolidated Statements of Operations.