Investments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Investments [Abstract]
Net realized investment gains (losses)	$ 42	$ 42	$ 8
Redemption senior notes		350	$ 350
Reduction of net unrealized gains on investments included in AOCI due to shadow adjustments	1,321	1,321		$ 1,014
Embedded derivative notional value	170	170		174
Embedded derivative fair value	(1)	(1)		$ 3
Future capital call commitments for limited partnership investments	405	405
Mortgage loan commitments	68	68
Commitments to purchase or fund privately placed debt securities	205	205
Commitments to sell various privately placed debt securities	$ 185	$ 185