Condensed Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Statement of Other Comprehensive Income [Abstract]
Net income (loss)	$ 75.1	$ 144.0
Unrealized gains/losses on securities	(169.5)	(72.4)
Other comprehensive income (loss), before tax:
Unrealized gains/losses on securities	(155.6)	(43.6)
Other-than-temporary impairments	0.9	1.6
Pension and other post-employment benefit liability	(0.6)	(0.6)
Other comprehensive income (loss), before tax	(169.2)	(71.4)
Income tax benefit (expense) related to items of other comprehensive income (loss)	(58.2)	(31.1)
Other comprehensive income (loss), after tax	(111.0)	(40.3)
Comprehensive income (loss)	$ (35.9)	$ 103.7