Condensed Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 67.6	$ 93.3	$ 219.6	$ 275.2
Unrealized gains/losses on securities	(52.9)	253.9	(862.3)	455.4
Other comprehensive income (loss), before tax:
Other-than-temporary impairments	2.0	7.0	3.4	10.6
Pension and other post-employment benefit liability	(0.7)	(0.6)	(1.7)	(1.7)
Other comprehensive income (loss), before tax	(51.6)	260.3	(860.6)	464.3
Income tax benefit (expense) related to items of other comprehensive income (loss)	(45.7)	98.2	(326.7)	157.6
Other comprehensive income (loss), after tax	(5.9)	162.1	(533.9)	306.7
Comprehensive income (loss)	$ 61.7	$ 255.4	$ (314.3)	$ 581.9