Investing Activities - Unrealized Investment Gains/Losses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Debt securities	$ 62.2	$ (1.9)
Other investments	0.1	0
Net unrealized investment gains (losses)	62.3	(1.9)
Applicable to DAC	16.7	(4.2)
Applicable to other actuarial offsets	34.5	15.6
Applicable to deferred income tax expense (benefit)	14.0	2.7
Offsets to net unrealized investment gains (losses)	65.2	14.1
Net unrealized investment gains (losses) included in OCI	$ (2.9)	$ (16.0)