Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	$ (315)	$ 400
Other comprehensive income (loss), before reclassifications	163	(793)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	21	(78)
Other comprehensive income (loss) after tax (expense) benefit	142	(715)
Accumulated other comprehensive income (loss), ending balance	(173)	(315)
Reclassification from AOCI, Current Period, Tax	(7)	49
Tax (expense) benefit on other comprehensive income (loss)	(121)	295
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	9	(23)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	6	(14)
Other comprehensive income (loss) after tax (expense) benefit	3	(9)
Accumulated other comprehensive income (loss), ending balance	30	27
Reclassification from AOCI, Current Period, Tax	(3)	8
Tax (expense) benefit on other comprehensive income (loss)	(1)	5
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	290	(595)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	38	(43)
Other comprehensive income (loss) after tax (expense) benefit	252	(552)
Accumulated other comprehensive income (loss), ending balance	642	390
Reclassification from AOCI, Current Period, Tax	(16)	30
Tax (expense) benefit on other comprehensive income (loss)	(117)	282
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	(22)	(36)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	(23)	(21)
Other comprehensive income (loss) after tax (expense) benefit	1	(15)
Accumulated other comprehensive income (loss), ending balance	(647)	(648)
Reclassification from AOCI, Current Period, Tax	12	11
Tax (expense) benefit on other comprehensive income (loss)	(3)	8
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	(114)	(139)
Amounts reclassified from accumulated other comprehensive income (loss) after tax (expense) benefit	0	0
Other comprehensive income (loss) after tax (expense) benefit	(114)	(139)
Accumulated other comprehensive income (loss), ending balance	(198)	(84)
Reclassification from AOCI, Current Period, Tax	0	0
Tax (expense) benefit on other comprehensive income (loss)	$ 0	$ 0