CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Cash Flows [Abstract]
Net income	$ 1,480	$ 1,314	$ 1,687
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion, net	234	248	248
Deferred income tax expense (benefit)	156	(34)	(131)
Share-based compensation	121	134	145
Net realized investment (gains) losses	(50)	(16)	(14)
Net trading (gains) losses	(7)	(6)	(7)
Loss from equity method investments	117	54	14
Other-than-temporary impairments and provision for loan losses	0	4	9
Net (gains) losses of consolidated investment entities	5	(38)	(132)
Changes in operating assets and liabilities:
Restricted and segregated investments	(198)	(24)	(401)
Deferred acquisition costs	(35)	55	(7)
Other investments, net	4	14	81
Policyholder account balances, future policy benefits and claims, net	(441)	8	494
Derivatives, net of collateral	595	59	93
Receivables	(457)	(150)	(277)
Brokerage deposits	(198)	310	337
Accounts payable and accrued expenses	206	173	82
Investment properties of consolidated investment entities	0	0	(114)
Other operating assets and liabilities of consolidated investment entities, net	0	(9)	95
Other, net	169	257	489
Net cash provided by (used in) operating activities	1,701	2,353	2,691
Available-for-Sale securities:
Proceeds from sales	454	366	294
Maturities, sinking fund payments and calls	4,957	4,421	4,542
Purchases	(5,419)	(6,498)	(4,562)
Proceeds from sales, maturities and repayments of mortgage loans	699	810	631
Funding of mortgage loans	(479)	(451)	(558)
Proceeds from sales and collections of other investments	269	253	236
Purchase of other investments	(487)	(291)	(306)
Purchase of investments by consolidated investment entities	(1,268)	(845)	(2,678)
Proceeds from sales, maturities and repayments of investments by consolidated investment entities	1,349	1,421	2,009
Purchase of land, buildings, equipment and software	(162)	(92)	(133)
Other, net	(112)	101	16
Net cash (used in) provided by investing activities	(199)	(805)	(509)
Investment certificates:
Proceeds from additions	4,725	4,250	3,139
Maturities, withdrawals and cash surrenders	(4,262)	(3,155)	(2,509)
Policyholder account balances:
Deposits and other additions	2,059	2,086	2,061
Net transfers to (from) separate accounts	(157)	127	(171)
Surrenders and other benefits	(1,893)	(1,932)	(2,714)
Cash paid for purchased options with deferred premiums	(282)	(341)	(392)
Cash received for purchased options with deferred premiums	116	276	16
Issuance of long-term debt, net of issuance costs	0	496	0
Repayments of long-term debt	(11)	(257)	(409)
Change in short-term borrowings, net	0	(1)	(1)
Dividends paid to shareholders	(491)	(479)	(465)
Repurchase of common shares	(1,485)	(1,707)	(1,741)
Exercise of stock options	15	9	16
Borrowings by consolidated investment entities	0	0	1,650
Repayments of debt by consolidated investment entities	(118)	(517)	(719)
Noncontrolling interests investments in subsidiaries	0	0	255
Distributions to noncontrolling interests	0	0	(415)
Other, net	(1)	3	3
Net cash provided by (used in) financing activities	(1,785)	(1,142)	(2,396)
Effect of exchange rate changes on cash	35	(75)	(21)
Net increase (decrease) in cash, cash equivalents and restricted cash	(248)	331	(235)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, beginning balance	5,392	5,407	5,642
Net cash outflows upon the deconsolidation of VIEs	0	(346)	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, ending balance	$ 5,144	$ 5,392	$ 5,407