Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	$ (315)	$ 400
Other comprehensive income (loss), before reclassifications	240	24
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	(19)	3
Other comprehensive income (loss) after tax (expense) benefit	259	21
Accumulated other comprehensive income (loss), ending balance	(56)	421
Reclassification from AOCI, Current Period, Tax	11	3
Tax (expense) benefit on other comprehensive income (loss)	(122)	(65)
Net unrealized gains (losses) on investments with OTTI losses [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	27	36
Other comprehensive income (loss), before reclassifications	3	(1)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	(2)	0
Other comprehensive income (loss) after tax (expense) benefit	5	(1)
Accumulated other comprehensive income (loss), ending balance	32	35
Reclassification from AOCI, Current Period, Tax	1	0
Tax (expense) benefit on other comprehensive income (loss)	(3)	0
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	390	942
Other comprehensive income (loss), before reclassifications	223	121
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	(11)	9
Other comprehensive income (loss) after tax (expense) benefit	234	112
Accumulated other comprehensive income (loss), ending balance	624	1,054
Reclassification from AOCI, Current Period, Tax	7	0
Tax (expense) benefit on other comprehensive income (loss)	(116)	(62)
Pension and postretirement benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(648)	(633)
Other comprehensive income (loss), before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	(6)	(6)
Other comprehensive income (loss) after tax (expense) benefit	6	6
Accumulated other comprehensive income (loss), ending balance	(642)	(627)
Reclassification from AOCI, Current Period, Tax	3	3
Tax (expense) benefit on other comprehensive income (loss)	(3)	(3)
Cumulative foreign currency translation adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(84)	55
Other comprehensive income (loss), before reclassifications	14	(96)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	0	0
Other comprehensive income (loss) after tax (expense) benefit	14	(96)
Accumulated other comprehensive income (loss), ending balance	(70)	(41)
Reclassification from AOCI, Current Period, Tax	0	0
Tax (expense) benefit on other comprehensive income (loss)	$ 0	$ 0