Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Statement of Cash Flows [Abstract]
Net cash provided by operating activities	$ 426.6	$ 962.8
Proceeds from the sale, maturity, disposal or redemption of:
Fixed maturities	2,277.2	1,678.5
Equity securities, available-for-sale	0.0	49.3
Mortgage loans on real estate	256.7	228.2
Limited partnerships/corporations	37.3	25.5
Acquisition of:
Fixed maturities	(1,897.6)	(2,548.5)
Equity securities, available-for-sale	(1.7)	0.0
Mortgage loans on real estate	(850.1)	(528.0)
Limited partnerships/corporations	(64.7)	(51.2)
Derivatives, net	168.8	(4.9)
Policy loans, net	5.3	7.1
Short-term investments, net	28.6	0.0
Collateral received (delivered), net	(160.7)	66.3
Net cash (used in) investing activities	(200.9)	(1,077.7)
Cash Flows from Financing Activities:
Deposits received for investment contracts	1,249.0	1,740.8
Maturities and withdrawals from investment contracts	(1,315.6)	(1,216.0)
Settlements on deposit contracts	(32.6)	(27.5)
Payments of Distributions to Affiliates	(261.0)	(274.0)
Net cash (used in) provided by financing activities	(360.2)	223.3
Net (decrease) increase in cash and cash equivalents	(134.5)	108.4
Cash and cash equivalents, beginning of year	561.0	661.1
Cash and cash equivalents, end of year	$ 426.5	$ 769.5