Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	$ 210	$ 143	$ (315)	$ 400
Other comprehensive income (loss), before reclassifications	52	(118)	566	(385)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	25	(35)	14	(45)
Other comprehensive income (loss) after tax (expense) benefit	27	(83)	552	(340)
Accumulated other comprehensive income (loss), ending balance	237	60	237	60
Reclassification from AOCI, Current Period, Tax	(12)	19	(4)	31
Tax (expense) benefit on other comprehensive income (loss)	(24)	18	(305)	113
Net unrealized gains (losses) on investments with OTTI losses [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	31	31	27	36
Other comprehensive income (loss), before reclassifications	7	2	9	(3)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	4	0	2	0
Other comprehensive income (loss) after tax (expense) benefit	3	2	7	(3)
Accumulated other comprehensive income (loss), ending balance	34	33	34	33
Reclassification from AOCI, Current Period, Tax	(2)	0	(1)	0
Tax (expense) benefit on other comprehensive income (loss)	(2)	(1)	(4)	1
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	934	689	390	942
Other comprehensive income (loss), before reclassifications	69	(67)	615	(318)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	27	(31)	29	(29)
Other comprehensive income (loss) after tax (expense) benefit	42	(36)	586	(289)
Accumulated other comprehensive income (loss), ending balance	976	653	976	653
Reclassification from AOCI, Current Period, Tax	(13)	17	(12)	22
Tax (expense) benefit on other comprehensive income (loss)	(19)	21	(292)	140
Pension and postretirement benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(637)	(585)	(648)	(633)
Other comprehensive income (loss), before reclassifications	0	0	0	36
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	(6)	(4)	(17)	(16)
Other comprehensive income (loss) after tax (expense) benefit	6	4	17	52
Accumulated other comprehensive income (loss), ending balance	(631)	(581)	(631)	(581)
Reclassification from AOCI, Current Period, Tax	3	2	9	9
Tax (expense) benefit on other comprehensive income (loss)	(3)	(2)	(9)	(28)
Cumulative foreign currency translation adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(118)	8	(84)	55
Other comprehensive income (loss), before reclassifications	(24)	(53)	(58)	(100)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	0	0	0	0
Other comprehensive income (loss) after tax (expense) benefit	(24)	(53)	(58)	(100)
Accumulated other comprehensive income (loss), ending balance	(142)	(45)	(142)	(45)
Reclassification from AOCI, Current Period, Tax	0	0	0	0
Tax (expense) benefit on other comprehensive income (loss)	$ 0	$ 0	$ 0	$ 0