Supplemental Unaudited Quarterly Financial Information Consolidated Balance Sheets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
ASSETS:
Available-for-sale debt securities, at fair value	$ 3,426.3	$ 3,252.1	$ 3,162.2	$ 3,054.7	$ 2,972.3
Short-term investments	81.0	55.0	165.0	224.9	244.9
Limited partnerships and other investments	10.5	10.3	7.2	5.7	6.7
Policy loans, at unpaid principal balances	66.1	65.6	62.8	61.5	61.0
Derivative instruments	237.8	190.7	199.3	186.6	149.4
Fair value investments	48.6	53.1	48.8	46.5	38.5
Total investments	3,870.3	3,626.8	3,645.3	3,579.9	3,472.8
Cash and cash equivalents	181.0	218.1	123.9	116.2	83.1	49.5	34.1
Accrued investment income	27.3	29.7	25.7	29.0	23.2
Receivables	8.6	14.3	8.6	9.8	16.2
Reinsurance recoverable		484.8	455.5	444.1
Deferred policy acquisition costs	462.3	458.5	463.1	433.6	426.2
Deferred income taxes, net	28.0	25.8	25.5	13.4	16.2
Receivable from related parties	2.6	2.0	6.0	0	0
Other assets	174.8	190.4	182.4	162.2	135.5
Separate account assets	2,052.7	2,049.5	2,021.3	2,109.5	2,061.8
Total assets	7,308.2	7,099.9	6,957.3	6,897.7	6,662.1
LIABILITIES:
Policy liabilities and accruals	1,899.0	1,974.9	1,926.5	1,930.8	1,876.2
Policyholder deposit funds	2,762.8	2,660.9	2,566.5	2,468.1	2,349.8
Payable to related parties	14.1	12.6	18.3	15.5	11.0
Other liabilities	177.1	143.7	161.4	115.1	68.2
Separate account liabilities	2,052.7	2,049.5	2,021.3	2,109.5	2,061.8
Total liabilities	6,935.7	6,841.6	6,694.0	6,639.0	6,367.0
COMMITMENTS AND CONTINGENT LIABILITIES (Note 16)
STOCKHOLDER’S EQUITY:
Common stock, $5,000 par value: 1,000 shares authorized; 500 shares issued	2.5	2.5	2.5	2.5	2.5
Additional paid-in capital	847.2	802.2	802.2	802.2	802.2
Accumulated other comprehensive income (loss)	(11.9)	5.6	(4.6)	(4.6)	11.4	2.6
Retained earnings (accumulated deficit)	(465.3)	(552.0)	(536.8)	(541.4)	(521.0)
Total stockholder’s equity	372.5	258.3	263.3	258.7	295.1	424.0	428.5
Total liabilities and stockholder’s equity	$ 7,308.2	$ 7,099.9	$ 6,957.3	$ 6,897.7	$ 6,662.1