Investing Activities - Unrealized Investment Gains/Losses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Debt securities	$ (1.9)	$ 20.3
Equity securities	0	0
Other investments	0	(0.3)
Net unrealized investment gains (losses)	(1.9)	20.0
Applicable to DAC	(4.2)	10.7
Applicable to other actuarial offsets	15.6	0.7
Applicable to deferred income tax expense (benefit)	2.7	3.7
Offsets to net unrealized investment gains (losses)	14.1	15.1
Net unrealized investment gains (losses) included in OCI	$ (16.0)	$ 4.9