Accumulated Other Comprehensive Income (Loss) Changes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Changes in Accumulated Other Comprehensive Income [Line Items]
Derivatives			$ 0.3	$ (4.8)
DAC/VOBA and sales inducements adjustment on available-for-sale securities			(191.7)	(392.4)
Other investments			0.2	0.2
Change in unrealized gains/losses on securities, before tax			469.1	47.1
Deferred income tax asset/liability			(284.7)	44.1
Change in unrealized gains/losses on securities, after tax			184.4	91.2
Change in OTTI, before tax			13.3	30.5
Deferred income tax asset/liability			(4.7)	(10.7)
Change in OTTI, after tax			8.6	19.8
Pension and other post-employment benefit liability, before tax	(0.1)	(0.1)	(0.2)	(0.2)
Deferred income tax asset/liability			0.1	0.1
Pension and other post-employment benefit liability, after tax			(0.1)	(0.1)
Other comprehensive income (loss), after tax	72.4	36.0	192.9	110.9
Fixed maturities
Changes in Accumulated Other Comprehensive Income [Line Items]
Unrealized holding gain (loss) on available-for-sale securities, before tax			657.9	452.4
Equity securities, available-for-sale
Changes in Accumulated Other Comprehensive Income [Line Items]
Unrealized holding gain (loss) on available-for-sale securities, before tax			$ 2.4	$ (8.3)