Deferred Policy Acquisition Costs (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Deferred Policy Acquisition Costs:
Balance, end of period	$ 435.6	$ 463.1	$ 462.3	$ 426.2
Policy acquisition costs deferred	24.0	16.0	61.2	49.6
Costs amortized to expenses:
Recurring costs	(19.5)	(21.7)	(61.3)	(59.7)
Assumption unlocking	0	0	0	0
Realized investment gains (losses)	(0.2)	(0.5)	8.9	(3.1)
Offsets to net unrealized investment gains or losses included in AOCI (1)	5.1	1.6	(26.1)	45.5
Balance, end of period	$ 445.0	$ 458.5	$ 445.0	$ 458.5