Condensed Financial Information (Parent Company) (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Cash Flows [Abstract]
Net cash provided by (used in) operating activities	$ 2,338	$ 3,621	$ 3,946
Cash flows from investing activities
Sales, maturities and repayments of fixed maturity securities	13,358	15,621	16,409
Sales, maturities and repayments of equity securities	57	22	97
Sales, maturities and repayments of mortgage loans	1,528	793	761
Sales, maturities and repayments of limited partnerships and limited liability companies	302	274	339
Purchases of fixed maturity securities	(16,406)	(16,427)	(17,811)
Purchases of equity securities	(22)	(2)	(2)
Purchases of mortgage loans	(3,609)	(3,890)	(2,044)
Purchases of limited partnerships and limited liability companies	(463)	(358)	(531)
Cash received in connection with freestanding derivatives	2,040	1,802	1,859
Cash paid in connection with freestanding derivatives	(2,638)	(2,938)	(3,829)
Sale of operating joint venture interest to a former affiliate	0	0	42
Net change in policy loans	126	105	(14)
Net change in short-term investments	(1,470)	269	1,057
Net change in other invested assets	36	(17)	(16)
Net cash provided by (used in) investing activities	(7,161)	(4,748)	(3,683)
Cash flows from financing activities
Policyholder account balances: Deposits	7,111	5,899	4,381
Policyholder account balances: Withdrawals	(2,773)	(3,400)	(3,114)
Net change in payables for collateral under securities loaned and other transactions	(673)	889	(3,139)
Long-term debt issued	412	228	0
Capital contribution	0	0	1,300
Capital contribution associated with the sale of operating joint venture interest to a former affiliate	0	0	202
Financing element on certain derivative instruments and other derivative related transactions, net	(203)	(303)	(149)
Other, net	(50)	(46)	0
Net cash provided by (used in) financing activities	3,822	3,258	(3,957)
Change in cash, cash equivalents and restricted cash	(1,001)	2,131	(3,694)
Cash, cash equivalents and restricted cash, beginning of year	3,494	1,363	5,057
Cash, cash equivalents and restricted cash, end of year	2,493	3,494	1,363
Supplemental disclosures of cash flow information
Net cash paid (received) for interest	30	3	81
Net cash paid (received) for income tax	3	(891)	(684)
Non-cash transactions:
Transfer of fixed maturity securities to former affiliate	0	0	293
Reduction of policyholder account balances in connection with reinsurance transactions	0	0	293
Parent Company
Statement of Cash Flows [Abstract]
Net cash provided by (used in) operating activities	2,160	2,774	3,460
Cash flows from investing activities
Sales, maturities and repayments of fixed maturity securities	12,009	14,909	14,667
Sales, maturities and repayments of equity securities	57	19	119
Sales, maturities and repayments of mortgage loans	1,434	840	704
Sales, maturities and repayments of limited partnerships and limited liability companies	302	254	333
Purchases of fixed maturity securities	(14,179)	(14,697)	(16,287)
Purchases of equity securities	(22)	(2)	(2)
Purchases of mortgage loans	(3,337)	(3,896)	(2,017)
Purchases of limited partnerships and limited liability companies	(463)	(358)	(531)
Cash received in connection with freestanding derivatives	1,933	1,795	1,858
Cash paid in connection with freestanding derivatives	(2,597)	(2,879)	(3,829)
Sale of operating joint venture interest to a former affiliate	0	0	67
Returns of capital and dividends from subsidiaries	54	25	551
Capital contributions to subsidiaries	(75)	0	(83)
Net change in policy loans	126	105	(14)
Net change in short-term investments	(1,418)	269	711
Net change in other invested assets	23	44	(41)
Net cash provided by (used in) investing activities	(6,153)	(3,572)	(3,794)
Cash flows from financing activities
Policyholder account balances: Deposits	6,117	5,064	3,845
Policyholder account balances: Withdrawals	(2,503)	(3,124)	(2,360)
Net change in payables for collateral under securities loaned and other transactions	(735)	871	(3,136)
Long-term debt issued	412	228	0
Capital contribution	0	0	1,300
Capital contribution associated with the sale of operating joint venture interest to a former affiliate	0	0	202
Financing element on certain derivative instruments and other derivative related transactions, net	(203)	(303)	(149)
Other, net	(7)	(2)	0
Net cash provided by (used in) financing activities	3,081	2,734	(298)
Change in cash, cash equivalents and restricted cash	(912)	1,936	(632)
Cash, cash equivalents and restricted cash, beginning of year	3,185	1,249	1,881
Cash, cash equivalents and restricted cash, end of year	2,273	3,185	1,249
Supplemental disclosures of cash flow information
Net cash paid (received) for interest	28	0	12
Net cash paid (received) for income tax	0	(168)	(421)
Non-cash transactions:
Transfer of fixed maturity securities from affiliate	0	417	0
Transfer of fixed maturity securities to former affiliate	0	0	293
Reduction of policyholder account balances in connection with reinsurance transactions	$ 0	$ 0	$ 293