Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net income (loss)	$ 1,253.2	$ 1,176.4	$ 936.1
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Amortization of deferred acquisition costs	270.8	367.2	187.1
Additions to deferred acquisition costs	(390.3)	(404.1)	(447.0)
Accrued investment income	(39.7)	26.2	52.3
Net cash flows for trading securities	(201.9)	(93.4)	(76.0)
Premiums due and other receivables	(211.5)	26.9	(131.9)
Contractholder and policyholder liabilities and dividends	3,283.6	1,634.0	1,614.7
Current and deferred income taxes (benefits)	(66.5)	175.9	211.7
Net realized capital (gains) losses	51.1	(14.7)	225.2
Depreciation and amortization expense	193.0	169.5	153.9
Mortgage loans held for sale, sold or repaid, net of gain		43.3	0.2
Real estate acquired through operating activities	(44.1)	(49.4)	(107.2)
Real estate sold through operating activities	53.7	158.9	24.2
Stock-based compensation	84.5	75.3	68.5
Other	141.2	(189.1)	(490.6)
Net adjustments	3,123.9	1,926.5	1,285.1
Net cash provided by (used in) operating activities	4,377.1	3,102.9	2,221.2
Investing activities
Available-for-sale securities: Purchases	(9,920.3)	(9,054.0)	(9,025.2)
Available-for-sale securities: Sales	1,563.0	2,512.0	1,919.1
Available-for-sale securities: Maturities	6,625.9	6,244.7	7,359.2
Mortgage loans acquired or originated	(2,275.1)	(2,169.6)	(2,192.9)
Mortgage loans sold or repaid	1,687.3	1,793.6	2,095.1
Real estate acquired	(322.0)	(281.7)	(85.6)
Net (purchases) sales of property and equipment	(136.4)	(136.0)	(59.4)
Purchases of interest in subsidiaries, net of cash acquired	(291.2)		(1,268.3)
Net change in other investments	(98.8)	(81.7)	31.7
Net cash provided by (used in) investing activities	(3,167.6)	(1,172.7)	(1,226.3)
Financing activities
Issuance of common stock	76.1	77.5	125.8
Acquisition of treasury stock	(300.6)	(222.7)	(153.6)
Proceeds from financing element derivatives	0.3	15.1	47.0
Payments for financing element derivatives	(82.0)	(58.0)	(48.0)
Excess tax benefits from share-based payment arrangements	15.7	9.7	10.1
Purchase of subsidiary shares from noncontrolling interest	(22.5)	(227.0)	(52.9)
Sale of subsidiary shares to noncontrolling interest			31.8
Dividends to common stockholders	(441.0)	(376.6)	(288.4)
Dividends to preferred stockholders	(16.5)	(33.0)	(33.0)
Preferred stock redemption	(550.0)
Issuance of long-term debt	804.9	38.5	38.2
Principal repayments of long-term debt	(52.6)	(100.3)	(218.2)
Net proceeds from (repayments of) short-term borrowings	157.0	(118.3)	108.0
Investment contract deposits	6,492.3	5,638.4	6,716.3
Investment contract withdrawals	(6,666.8)	(7,099.2)	(8,852.7)
Net increase (decrease) in banking operation deposits	91.1	30.7	(225.7)
Other	(14.0)	(12.9)	(5.0)
Net cash provided by (used in) financing activities	(508.6)	(2,438.1)	(2,800.3)
Net increase (decrease) in cash and cash equivalents	700.9	(507.9)	(1,805.4)
Cash and cash equivalents at beginning of period	1,863.9	2,371.8	4,177.2
Cash and cash equivalents at end of period	2,564.8	1,863.9	2,371.8
Supplemental Information:
Cash paid for interest	149.6	137.6	144.1
Cash paid for income taxes	$ 129.6	$ 73.8	$ 61.2