Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Cash Flows [Abstract]
Net income (loss)	$ 112.8	$ 173.2	$ 231.7
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Capitalization of deferred policy acquisition costs, value of business acquired and sales inducements	(79.5)	(83.5)	(77.4)
Net amortization of deferred policy acquisition costs, value of business acquired and sales inducements	167.8	133.9	110.9
Net accretion/amortization of discount/premium	(0.7)	7.1	9.6
Future policy benefits, claims reserves and interest credited	1,288.6	1,193.5	616.7
Deferred income tax (benefit) expense	(2.6)	(1.3)	(11.2)
Net realized capital losses	213.2	277.2	139.6
Depreciation	3.6	3.6	3.6
Change in:
Accrued investment income	(6.2)	(10.1)	(0.2)
Premiums receivable and reinsurance recoverable	205.1	90.7	87.1
Other receivables and asset accruals	6.9	2.0	(59.0)
Due to/from affiliates	29.5	25.7	(8.2)
Other payables and accruals	126.5	(56.8)	71.0
Other, net	(11.1)	0.2	(10.6)
Net cash provided by operating activities	2,053.9	1,755.4	1,103.6
Proceeds from the sale, maturity, disposal or redemption of:
Fixed maturities	3,184.3	3,372.8	3,071.1
Equity securities, available-for-sale	49.3	17.4	14.1
Mortgage loans on real estate	375.3	557.2	504.6
Limited partnerships/corporations	70.8	47.8	43.9
Acquisition of:
Fixed maturities	(5,663.9)	(5,257.7)	(3,300.6)
Equity securities, available-for-sale	0.0	(28.0)	0.0
Mortgage loans on real estate	(900.5)	(773.3)	(621.3)
Limited partnerships/corporations	(113.2)	(95.7)	(103.1)
Derivatives, net	28.4	(46.7)	(25.2)
Policy loans, net	10.9	9.3	2.9
Short-term investments, net	(32.9)	241.5	(226.4)
Collateral received (delivered), net	(30.1)	8.1	163.1
Purchases of fixed assets, net	0.0	(0.1)	0.0
Net cash used in investing activities	(3,021.6)	(1,947.4)	(476.9)
Cash Flows from Financing Activities:
Deposits received for investment contracts	3,746.0	3,195.1	2,355.5
Maturities and withdrawals from investment contracts	(2,534.5)	(2,439.7)	(2,580.4)
Receipts on deposit contracts	0.0	0.0	124.7
Settlements on deposit contracts	(66.0)	(63.2)	(54.9)
Excess tax benefits on share-based compensation	0.1	0.7	1.7
Dividends paid and return of capital distribution	(278.0)	(321.0)	(371.0)
Net cash provided by (used in) financing activities	867.6	371.9	(524.4)
Net (decrease) increase in cash and cash equivalents	(100.1)	179.9	102.3
Cash and cash equivalents, beginning of year	661.1	481.2	378.9
Cash and cash equivalents, end of year	561.0	661.1	481.2
Supplemental cash flow information:
Income taxes paid (received), net	15.4	54.2	168.3
Interest paid	$ 0.0	$ 0.1	$ 0.0