Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	$ (56)	$ 421	$ (315)	$ 400
Other comprehensive income (loss), before reclassifications	274	(291)	514	(267)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	8	(13)	(11)	(10)
Other comprehensive income (loss) after tax (expense) benefit	266	(278)	525	(257)
Accumulated other comprehensive income (loss), ending balance	210	143	210	143
Reclassification from AOCI, Current Period, Tax	(3)	9	8	12
Tax (expense) benefit on other comprehensive income (loss)	(159)	160	(281)	95
Net unrealized gains (losses) on investments with OTTI losses [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	32	35	27	36
Other comprehensive income (loss), before reclassifications	(1)	(4)	2	(5)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	0	0	(2)	0
Other comprehensive income (loss) after tax (expense) benefit	(1)	(4)	4	(5)
Accumulated other comprehensive income (loss), ending balance	31	31	31	31
Reclassification from AOCI, Current Period, Tax	0	0	1	0
Tax (expense) benefit on other comprehensive income (loss)	1	2	(2)	2
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	624	1,054	390	942
Other comprehensive income (loss), before reclassifications	323	(372)	546	(251)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	13	(7)	2	2
Other comprehensive income (loss) after tax (expense) benefit	310	(365)	544	(253)
Accumulated other comprehensive income (loss), ending balance	934	689	934	689
Reclassification from AOCI, Current Period, Tax	(6)	5	1	5
Tax (expense) benefit on other comprehensive income (loss)	(157)	181	(273)	119
Pension and postretirement benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(642)	(627)	(648)	(633)
Other comprehensive income (loss), before reclassifications	0	36	0	36
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	(5)	(6)	(11)	(12)
Other comprehensive income (loss) after tax (expense) benefit	5	42	11	48
Accumulated other comprehensive income (loss), ending balance	(637)	(585)	(637)	(585)
Reclassification from AOCI, Current Period, Tax	3	4	6	7
Tax (expense) benefit on other comprehensive income (loss)	(3)	(23)	(6)	(26)
Cumulative foreign currency translation adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(70)	(41)	(84)	55
Other comprehensive income (loss), before reclassifications	(48)	49	(34)	(47)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	0	0	0	0
Other comprehensive income (loss) after tax (expense) benefit	(48)	49	(34)	(47)
Accumulated other comprehensive income (loss), ending balance	(118)	8	(118)	8
Reclassification from AOCI, Current Period, Tax	0	0	0	0
Tax (expense) benefit on other comprehensive income (loss)	$ 0	$ 0	$ 0	$ 0