Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net income	$ 2,469.8	$ 2,560.0	$ 2,569.7
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized gains on financial instruments	(4.9)	(157.5)	(177.0)
Other-than-temporary impairment losses recognized in income	115.4	83.4	49.0
(Gain) loss on extinguishment of debt	0.0	(9.3)	81.1
Gain on disposal from discontinued operations	0.0	0.0	(3.2)
Loss (gain) on disposal of assets	4.5	16.0	(1.7)
Deferred income taxes	126.9	(65.9)	30.7
Amortization, net of accretion	807.8	802.1	744.5
Depreciation expense	104.0	105.8	106.5
Impairment of property and equipment	44.8	1.8	7.9
Share-based compensation	164.6	148.2	168.9
Excess tax benefits from share-based compensation	(53.5)	(95.8)	(46.4)
Changes in operating assets and liabilities:
Receivables, net	(1,380.5)	(42.9)	(1,899.7)
Other invested assets	(19.4)	5.9	(21.7)
Other assets	(127.7)	33.8	405.5
Policy liabilities	321.7	193.0	1,240.6
Unearned income	(173.6)	33.9	255.1
Accounts payable and accrued expenses	116.6	(219.3)	(14.4)
Other liabilities	605.7	686.4	(7.9)
Income taxes	178.8	41.5	(34.0)
Other, net	(96.5)	(5.1)	(84.2)
Net cash provided by operating activities	3,204.5	4,116.0	3,369.3
Investing activities
Purchases of fixed maturity securities	(10,157.7)	(9,792.0)	(9,613.4)
Proceeds from fixed maturity securities:
Sales	8,636.0	8,909.2	8,066.0
Maturities, calls and redemptions	1,418.6	1,313.6	1,318.7
Purchases of equity securities	(1,476.3)	(1,561.4)	(912.0)
Proceeds from sales of equity securities	1,592.8	1,471.1	746.5
Purchases of other invested assets	(433.1)	(505.8)	(205.7)
Proceeds from sales of other invested assets	304.9	85.9	124.7
Changes in collateral and settlement of non-hedging derivatives	(34.5)	(36.5)	(67.4)
Changes in securities lending collateral	222.0	214.4	(545.6)
Purchases of subsidiaries, net of cash acquired	0.0	(638.9)	0.0
Proceeds from sale of subsidiary, net of cash sold	0.0	0.0	740.0
Purchases of property and equipment	(583.6)	(638.2)	(714.6)
Proceeds from sales of property and equipment	0.0	35.3	88.0
Other, net	(3.0)	(8.2)	(0.1)
Net cash used in investing activities	(513.9)	(1,151.5)	(974.9)
Financing activities
Net (repayments of) proceeds from commercial paper borrowings	(53.2)	682.2	(379.2)
Proceeds from long-term borrowings	0.0	1,226.5	2,700.0
Repayments of long-term borrowings	0.0	(2,697.2)	(1,730.1)
Proceeds from short-term borrowings	2,400.0	2,760.0	2,050.0
Repayments of short-term borrowings	(2,500.0)	(2,620.0)	(2,050.0)
Changes in securities lending payable	(222.0)	(214.4)	545.6
Changes in bank overdrafts	513.8	(243.8)	173.0
Premiums paid on equity call options	0.0	(16.7)	0.0
Proceeds from sale of put options	0.0	16.6	0.0
Repurchase and retirement of common stock	0.0	(1,515.8)	(2,998.8)
Change in collateral and settlements of debt-related derivatives	(360.4)	0.0	0.0
Cash dividends	(684.0)	(656.6)	(480.7)
Proceeds from issuance of common stock under employee stock plans	119.4	186.0	301.3
Excess tax benefits from share-based compensation	53.5	95.8	46.4
Net cash used in financing activities	(732.9)	(2,997.4)	(1,822.5)
Effect of foreign exchange rates on cash and cash equivalents	4.1	(5.3)	(7.1)
Change in cash and cash equivalents	1,961.8	(38.2)	564.8
Cash and cash equivalents at beginning of year	2,113.5	2,151.7	1,586.9
Cash and cash equivalents at end of year	$ 4,075.3	$ 2,113.5	$ 2,151.7