Schedule II-Condensed Financial Information Of Registrant (Statement Of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net income	$ 934	$ 1,183	$ 1,139	$ 1,551	$ 424	$ 960	$ 1,054	$ 1,312		$ 4,807	$ 3,750	$ 3,843
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized gains (losses) on financial instruments										(131)	203	(200)
Other-than-temporary impairment losses recognized in income										47	26	33
Loss on extinguishment of debt										2	11	282
Loss on disposal of assets										3	13	15
Deferred income taxes										81	91	(1,272)
Amortization, net of accretion										986	1,008	780
Depreciation expense										147	124	111
Share-based compensation										294	226	170
Changes in operating assets and liabilities:
Receivables, net										(1,053)	(695)	(22)
Other invested assets, current										(48)	(1)	(36)
Other assets										(170)	(26)	(629)
Accounts payable and accrued expenses										(593)	122	922
Other liabilities										148	(25)	(120)
Other, net										(92)	(205)	(165)
Net cash provided by operating activities										6,061	3,827	4,185
Investing activities
Changes in collateral and settlement of non-hedging derivatives										0	0	65
Changes in securities lending collateral										254	(149)	625
Other, net										(50)	(71)	12
Net cash used in investing activities										(2,792)	(1,259)	(5,082)
Financing activities
Net (repayments of) proceeds from commercial paper borrowings										(297)	(107)	175
Proceeds from long-term borrowings										2,473	835	5,458
Repayments of long-term borrowings										(1,123)	(1,684)	(2,815)
Changes in securities lending payable										(254)	150	(625)
Changes in bank overdrafts										(169)	(210)	71
Premiums paid on equity call options									$ 0	(1)	0
Proceeds from sale of put options										0	1	1
Proceeds from issuance of common stock under Equity Units stock purchase agreements										0	1,250	0
Repurchase and retirement of common stock										(1,701)	(1,685)	(1,998)
Change in collateral and settlements of debt-related derivatives										(34)	23	(149)
Cash dividends	(202)	$ (204)	$ (206)	(206)	(193)	$ (195)	$ (196)	(192)		(818)	(776)	(705)
Proceeds from issuance of common stock under employee stock plans										187	173	225
Taxes paid through withholding of common stock under employee stock plans										(84)	(81)	(46)
Net cash (used in) provided by financing activities										(2,266)	(2,241)	427
Change in cash and cash equivalents										1,003	325	(466)
Cash and cash equivalents at beginning of year				3,934				3,609	4,075	3,934	3,609	4,075
Cash and cash equivalents at end of year	4,937				3,934					4,937	3,934	3,609
Parent Company [Member]
Operating activities
Net income										4,807	3,750	3,843
Adjustments to reconcile net income to net cash provided by operating activities:
Undistributed earnings of subsidiaries										(1,561)	(744)	(2,437)
Net realized gains (losses) on financial instruments										65	46	18
Other-than-temporary impairment losses recognized in income										20	15	7
Loss on extinguishment of debt										2	11	283
Deferred income taxes										2	(43)	(33)
Amortization, net of accretion										37	43	25
Depreciation expense										69	70	69
Share-based compensation										294	226	170
Changes in operating assets and liabilities:
Receivables, net										41	(73)	(17)
Other invested assets, current										6	(5)	(1)
Other assets										(235)	(225)	(102)
Amounts due (from)/ to subsidiaries										(432)	2,259	(1,034)
Accounts payable and accrued expenses										(608)	303	491
Other liabilities										186	154	(61)
Income taxes										(282)	187	(6)
Other, net										0	1	(2)
Net cash provided by operating activities										2,411	5,975	1,213
Investing activities
Purchases of investments										(9,682)	(800)	(3,814)
Proceeds from sales, maturities, calls and redemptions of investments										9,457	1,865	2,595
Changes in collateral and settlement of non-hedging derivatives										0	0	65
Capitalization of subsidiaries										(232)	(4,379)	(124)
Changes in securities lending collateral										18	(21)	25
Purchases of property and equipment, net of sales										(54)	(137)	(44)
Other, net										0	4	18
Net cash used in investing activities										(493)	(3,468)	(1,279)
Financing activities
Net (repayments of) proceeds from commercial paper borrowings										(297)	(107)	175
Proceeds from long-term borrowings										2,473	835	5,458
Repayments of long-term borrowings										(1,123)	(1,684)	(2,815)
Changes in securities lending payable										(18)	21	(25)
Changes in bank overdrafts										64	(107)	51
Premiums paid on equity call options										(1)	0	0
Proceeds from sale of put options										0	1	1
Proceeds from issuance of common stock under Equity Units stock purchase agreements										0	1,250	0
Repurchase and retirement of common stock										(1,701)	(1,685)	(1,998)
Change in collateral and settlements of debt-related derivatives										(34)	23	(149)
Cash dividends										(856)	(812)	(737)
Proceeds from issuance of common stock under employee stock plans										187	173	225
Taxes paid through withholding of common stock under employee stock plans										(84)	(81)	(47)
Net cash (used in) provided by financing activities										(1,390)	(2,173)	139
Change in cash and cash equivalents										528	334	73
Cash and cash equivalents at beginning of year				$ 1,290				$ 956	$ 883	1,290	956	883
Cash and cash equivalents at end of year	$ 1,818				$ 1,290					$ 1,818	$ 1,290	$ 956