Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pre-tax
Unrealized net holding gains and losses arising during the period, net of related offsets	$ (1,896)	$ 1,026	$ (1,278)
Less: reclassification adjustment of realized capital gains and losses	112	597	549
Unrealized net capital gains and losses	(2,008)	429	(1,827)
Unrealized foreign currency translation adjustments	(89)	(62)	(49)
Unrecognized pension and other postretirement benefit cost arising during the period	(64)	(1,197)	1,231
Less: reclassification adjustment of net periodic cost recognized in operating costs and expenses	(134)	(78)	(445)
Unrecognized pension and other postretirement benefit cost	70	(1,119)	1,676
Other comprehensive loss	(2,027)	(752)	(200)
Tax
Unrealized net holding gains and losses arising during the period, net of related offsets	663	(358)	447
Less: reclassification adjustment of realized capital gains and losses	(39)	(209)	(192)
Unrealized net capital gains and losses	702	(149)	639
Unrealized foreign currency translation adjustments	31	22	17
Unrecognized pension and other postretirement benefit cost arising during the period	25	421	(429)
Less: reclassification adjustment of net periodic cost recognized in operating costs and expenses	47	27	156
Unrecognized pension and other postretirement benefit cost	(22)	394	(585)
Other comprehensive loss	711	267	71
After-tax
Unrealized net holding gains and losses arising during the period, net of related offsets	(1,233)	668	(831)
Less: reclassification adjustment of realized capital gains and losses	73	388	357
Unrealized net capital gains and losses	(1,306)	280	(1,188)
Unrealized foreign currency translation adjustments	(58)	(40)	(32)
Unrecognized pension and other postretirement benefit cost arising during the period	(39)	(776)	802
Less: reclassification adjustment of net periodic cost recognized in operating costs and expenses	(87)	(51)	(289)
Unrecognized pension and other postretirement benefit cost	48	(725)	1,091
Other comprehensive loss, after-tax	$ (1,316)	$ (485)	$ (129)