Derivatives (Changes in Estimated Fair Value Related to Embedded Derivatives) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives gains (losses)	$ 69	$ (4,624)	$ 647	$ (5,793)
Net derivative gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives gains (losses)	69	(4,624)	647	(5,793)
Policyholder benefits and claims
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives gains (losses)	$ 14	$ 60	$ (1)	$ 105