Investing Activities Schedule of Unrealized Loss on Investments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Debt securities	$ 135.4	$ (149.4)	$ 123.1
Equity securities	1.2	(0.9)	0
Other investments	0.3	(0.8)	0
Net unrealized investment gains	136.9	(151.1)	123.1
Net unrealized investment gains	136.9	(151.1)	123.1
Applicable deferred policy acquisition cost	38.0	(61.3)	32.0
Applicable other actuarial offsets	50.3	(56.7)	59.2
Applicable deferred income tax expense (benefit)	31.9	(11.6)	24.3
Offsets to net unrealized investment gains (losses)	120.2	(129.6)	115.5
Net unrealized investment gains included in OCI	$ 16.7	$ (21.5)	$ 7.6