Deferred Policy Acquisition Costs (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Deferred Policy Acquisition Costs:
Policy acquisition costs deferred	$ 16.4	$ 19.3	$ 33.5	$ 43.3
Costs amortized to expenses:
Recurring costs	(21.3)	(38.8)	(38.0)	(73.1)
Realized investment gains (losses)	(5.3)	11.2	(2.6)	4.8
Offsets to net unrealized investment gains or losses included in AOCI (1)	39.7	(20.7)	44.0	(31.4)
Change in deferred policy acquisition costs	29.5	(29.0)	36.9	(56.4)
Deferred policy acquisition costs, beginning of period	433.6	461.7	426.2	489.1
Deferred policy acquisition costs, end of period	$ 463.1	$ 432.7	$ 463.1	$ 432.7