Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities
Net income	$ 1,009.9	$ 703.0
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized (gains) losses on financial instruments	(7.3)	125.1
Other-than-temporary impairment losses recognized in income	8.1	66.9
Loss on disposal of assets	0.7	0.2
Deferred income taxes	(157.2)	73.3
Amortization, net of accretion	193.4	199.7
Depreciation expense	27.3	25.6
Share-based compensation	42.7	37.6
Excess tax benefits from share-based compensation	0.0	(39.8)
Changes in operating assets and liabilities:
Receivables, net	276.3	(170.5)
Other invested assets	(14.8)	(5.3)
Other assets	(205.2)	(117.4)
Policy liabilities	130.1	(27.2)
Unearned income	954.2	(124.2)
Accounts payable and accrued expenses	(223.8)	66.3
Other liabilities	40.3	39.5
Income taxes	659.7	507.7
Other, net	(46.2)	(0.7)
Net cash provided by operating activities	2,688.2	1,359.8
Investing activities
Purchases of fixed maturity securities	(4,030.1)	(3,287.1)
Proceeds from fixed maturity securities:
Sales	2,851.8	2,507.0
Maturities, calls and redemptions	522.7	249.3
Purchases of equity securities	(367.0)	(747.1)
Proceeds from sales of equity securities	63.0	206.5
Purchases of other invested assets	(73.7)	(146.4)
Proceeds from sales of other invested assets	76.5	99.3
Change in collateral and settlements of non-hedging derivatives	0.4	(0.6)
Changes in securities lending collateral	(154.5)	(154.4)
Purchases of property and equipment	(127.9)	(117.5)
Other, net	11.8	0.0
Net cash used in investing activities	(1,227.0)	(1,391.0)
Financing activities
Net proceeds from (repayments of) commercial paper borrowings	1,719.1	(77.3)
Repayments of long-term borrowings	(401.1)	0.0
Proceeds from short-term borrowings	1,170.0	980.0
Repayments of short-term borrowings	(1,070.0)	(980.0)
Changes in securities lending payable	154.5	154.4
Changes in bank overdrafts	(168.9)	(113.2)
Repurchase and retirement of common stock	(50.7)	0.0
Change in collateral and settlements of debt-related derivatives	(8.0)	(237.1)
Cash dividends	(172.2)	(170.7)
Proceeds from issuance of common stock under employee stock plans	103.5	50.9
Taxes paid through withholding of common stock under employee stock plans	(41.9)	(55.5)
Excess tax benefits from share-based compensation	0.0	39.8
Net cash provided by (used in) financing activities	1,234.3	(408.7)
Effect of foreign exchange rates on cash and cash equivalents	1.6	2.4
Change in cash and cash equivalents	2,697.1	(437.5)
Cash and cash equivalents at beginning of period	4,075.3	2,113.5
Cash and cash equivalents at end of period	$ 6,772.4	$ 1,676.0