Condensed Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 74.6	$ 76.9	$ 120.3	$ 152.0
Other comprehensive income (loss), before tax:
Unrealized gains/losses on securities	253.5	(639.9)	569.4	(809.4)
Other-than-temporary impairments	0.7	0.5	7.3	1.4
Pension and other post-employment benefit liability	(0.5)	(0.4)	(1.1)	(1.0)
Other comprehensive income (loss), before tax	253.7	(639.8)	575.6	(809.0)
Income tax expense (benefit) related to items of other comprehensive income (loss)	87.0	(222.8)	199.4	(281.0)
Other comprehensive income (loss), after tax	166.7	(417.0)	376.2	(528.0)
Comprehensive income (loss)	$ 241.3	$ (340.1)	$ 496.5	$ (376.0)