Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net income	$ 3,189	$ 1,877	$ 2,171
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other non-cash items	483	382	371
Realized capital gains and losses	(445)	90	(30)
Gain on disposition of operations	(20)	(5)	(3)
Interest credited to contractholder funds	690	726	761
Goodwill impairment	125	0	0
Changes in:
Policy benefits and other insurance reserves	302	631	473
Unearned premiums	463	362	638
Deferred policy acquisition costs	(214)	(165)	(239)
Premium installment receivables, net	(131)	(42)	(134)
Reinsurance recoverables, net	(211)	(264)	(178)
Income taxes	(245)	417	(119)
Other operating assets and liabilities	328	(16)	(95)
Net cash provided by operating activities	4,314	3,993	3,616
Proceeds from sales
Fixed income securities	25,341	25,061	28,693
Equity securities	6,504	5,546	3,754
Limited partnership interests	1,125	881	1,101
Mortgage loans	0	0	6
Other investments	274	262	545
Investment collections
Fixed income securities	4,194	4,533	4,432
Mortgage loans	600	501	538
Other investments	642	421	293
Investment purchases
Fixed income securities	(31,145)	(27,990)	(30,758)
Equity securities	(6,585)	(5,950)	(4,960)
Limited partnership interests	(1,440)	(1,450)	(1,343)
Mortgage loans	(646)	(646)	(687)
Other investments	(999)	(885)	(902)
Change in short-term investments, net	2,610	(2,446)	385
Change in other investments, net	(30)	(51)	(52)
Purchases of property and equipment, net	(299)	(313)	(303)
Acquisition of operations	(1,356)	0	0
Net cash (used in) provided by investing activities	(1,210)	(2,526)	742
Cash flows from financing activities
Proceeds from issuance of long-term debt	0	1,236	0
Repayments of long-term debt	0	(17)	(20)
Contractholder fund deposits	1,025	1,049	1,052
Contractholder fund withdrawals	(1,890)	(2,087)	(2,327)
Dividends paid on common stock	(525)	(486)	(483)
Dividends paid on preferred stock	(116)	(116)	(116)
Treasury stock purchases	(1,495)	(1,337)	(2,808)
Shares reissued under equity incentive plans, net	135	164	130
Excess tax benefits on share-based payment arrangements	0	32	45
Other	(57)	36	7
Net cash used in financing activities	(2,923)	(1,526)	(4,520)
Net increase (decrease) in cash	181	(59)	(162)
Cash at beginning of year	436	495	657
Cash at end of year	$ 617	$ 436	$ 495