Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Cash Flows [Abstract]
Net cash provided by operating activities	$ 133.1	$ 523.6
Proceeds from the sale, maturity, disposal or redemption of:
Fixed maturities	1,445.8	906.7
Equity securities, available-for-sale	0.0	49.3
Mortgage loans on real estate	145.1	77.7
Limited partnerships/corporations	21.6	14.8
Acquisition of:
Fixed maturities	(890.7)	(1,305.5)
Equity securities, available-for-sale	(1.7)	0.0
Mortgage loans on real estate	(635.8)	(278.5)
Limited partnerships/corporations	(30.2)	(25.2)
Derivatives, net	168.5	11.1
Policy loans, net	4.5	4.6
Short-term investments, net	28.9	0.0
Short-term loans to affiliates, net	(100.0)	(12.0)
Collateral received (delivered), net	(152.4)	58.5
Purchases of fixed assets, net	0.0	(0.1)
Net cash provided by (used in) investing activities	3.6	(498.6)
Cash Flows from Financing Activities:
Deposits received for investment contracts	679.5	830.2
Maturities and withdrawals from investment contracts	(791.8)	(615.5)
Settlements on deposit contracts	(16.7)	(13.8)
Net cash (used in) provided by financing activities	(129.0)	200.9
Net increase in cash and cash equivalents	7.7	225.9
Cash and cash equivalents, beginning of year	561.0	661.1
Cash and cash equivalents, end of year	$ 568.7	$ 887.0