Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	$ (1,711)
Other comprehensive income (loss) attributable to redeemable noncontrolling interests	(5)	$ (15)	$ (3)
Accumulated other comprehensive income (loss), ending	(941)	(1,711)
Securities and Derivatives [ Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	18	383	365
Other comprehensive income (loss) before reclassifications, pre-tax	1,266	(512)	34
Other comprehensive income (loss) before reclassifications, tax (expense) benefit	(270)	100	(19)
Other comprehensive income (loss) before reclassifications, after-tax	996	(412)	15
Reclassification adjustment, tax (expense) benefit	10	(13)	28
Reclassification adjustment, after-tax	(39)	(47)	52
Shareholders' other comprehensive income (loss), net of tax	957	(365)	(37)
Accumulated other comprehensive income (loss), ending	975	18	383
Securities and Derivatives [ Member] | Previously Reported [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	18	328	365
Accumulated other comprehensive income (loss), ending		18	328
Securities and Derivatives [ Member] | Restatement Adjustment [Member] | Reclassification adjustment to retained earnings related to U.S. tax reform legislation [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	0	65	0
Accumulated other comprehensive income (loss), ending		0	65
Securities and Derivatives [ Member] | Restatement Adjustment [Member] | Reclassification adjustment to retained earnings related to new financial instruments guidance [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	0	(4)	0
Accumulated other comprehensive income (loss), ending		0	(4)
Securities and Derivatives [ Member] | Restatement Adjustment [Member] | Reclassification adjustment to retained earnings related to new hedging guidance [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	0	(6)	0
Accumulated other comprehensive income (loss), ending		0	(6)
Securities and Derivatives [ Member] | Selling, general and administrative expenses [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Reclassification adjustment, pre-tax	0	0	1
Securities and Derivatives [ Member] | Net Realized Investment Gains [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Reclassification adjustment, pre-tax	(49)	60	(81)
Translation of foreign currencies [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	(221)	(69)	(369)
Other comprehensive income (loss) before reclassifications, pre-tax	(57)	(167)	306
Other comprehensive income (loss) before reclassifications, tax (expense) benefit	(2)	0	(5)
Other comprehensive income (loss) before reclassifications, after-tax	(59)	(167)	301
Other comprehensive income (loss) attributable to redeemable noncontrolling interests	(5)	(15)	(3)
Shareholders' other comprehensive income (loss), net of tax	(54)	(152)	304
Accumulated other comprehensive income (loss), ending	(275)	(221)	(69)
Translation of foreign currencies [Member] | Previously Reported [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	(221)	(65)	(369)
Accumulated other comprehensive income (loss), ending		(221)	(65)
Translation of foreign currencies [Member] | Restatement Adjustment [Member] | Reclassification adjustment to retained earnings related to U.S. tax reform legislation [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	0	(4)	0
Accumulated other comprehensive income (loss), ending		0	(4)
Postretirement benefits liability [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	(1,508)	(1,635)	(1,378)
Other comprehensive income (loss) before reclassifications, pre-tax	(249)	93	(22)
Other comprehensive income (loss) before reclassifications, tax (expense) benefit	59	(20)	8
Other comprehensive income (loss) before reclassifications, after-tax	(190)	73	(14)
Reclassification adjustment, tax (expense) benefit	(15)	(15)	(24)
Reclassification adjustment, after-tax	57	54	47
Shareholders' other comprehensive income (loss), net of tax	(133)	127	33
Accumulated other comprehensive income (loss), ending	(1,641)	(1,508)	(1,635)
Postretirement benefits liability [Member] | Previously Reported [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	(1,508)	(1,345)	(1,378)
Accumulated other comprehensive income (loss), ending		(1,508)	(1,345)
Postretirement benefits liability [Member] | Restatement Adjustment [Member] | Reclassification adjustment to retained earnings related to U.S. tax reform legislation [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning	0	(290)	0
Accumulated other comprehensive income (loss), ending		0	(290)
Reclassification adjustment for amortization of net losses from past experience and prior service costs [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Reclassification adjustment, pre-tax	62	69	64
Reclassification adjustment for settlement losses [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Reclassification adjustment, pre-tax	$ 10	$ 0	$ 7