Condensed Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Statement of Cash Flows [Abstract]
Net cash provided by operating activities	$ 732.3	$ 897.0
Proceeds from the sale, maturity, disposal or redemption of:
Fixed maturities	2,215.0	2,609.2
Equity securities, available-for-sale	14.1	0.7
Mortgage loans on real estate	314.1	177.6
Limited partnerships/corporations	34.9	22.6
Acquisition of:
Fixed maturities	(2,290.6)	(3,287.4)
Equity securities, available-for-sale	0	(0.8)
Mortgage loans on real estate	(482.6)	(587.8)
Limited partnerships/corporations	(93.2)	(16.5)
Derivatives, net	(22.9)	(222.0)
Policy loans, net	1.8	(1.2)
Short-term investments, net	(6.3)	447.3
Collateral received	103.2	(32.3)
Purchases of fixed assets, net	0	(0.2)
Net cash used in investing activities	(212.5)	(890.8)
Cash Flows from Financing Activities:
Deposits received for investment contracts	1,669.9	2,042.7
Maturities and withdrawals from investment contracts	(1,946.3)	(1,917.7)
Receipts on deposit contracts	124.7	87.1
Settlements on deposit contracts	(36.2)	(8.5)
Dividends paid and return of capital distribution	(281.0)	(174.0)
Net cash (used in) provided by financing activities	(468.9)	29.6
Net increase in cash and cash equivalents	50.9	35.8
Cash and cash equivalents, beginning of year	378.9	363.4
Cash and cash equivalents, end of year	$ 429.8	$ 399.2