Condensed Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 76.9	$ 37.9	$ 152.0	$ 181.9
Other comprehensive income (loss), before tax:
Unrealized gains/losses on securities	(639.9)	273.9	(809.4)	201.5
Other-than-temporary impairments	0.5	2.0	1.4	3.6
Pension and other post-employment benefit liability	(0.4)	(0.5)	(1.0)	(1.1)
Other comprehensive income (loss), before tax	(639.8)	275.4	(809.0)	204.0
Income tax benefit (expense) related to items of other comprehensive income (loss)	(222.8)	90.5	(281.0)	59.4
Other comprehensive income (loss), after tax	(417.0)	184.9	(528.0)	144.6
Comprehensive income (loss)	$ (340.1)	$ 222.8	$ (376.0)	$ 326.5