Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 31.3	$ 74.0	$ 51.8	$ 136.0
Other comprehensive income (loss), before tax:
Unrealized gains/losses on securities	447.4	(580.9)	964.9	(374.4)
Other-than-temporary impairments	0.4	0.5	0.8	1.7
Pension and other post-employment benefit liability	(0.5)	(0.5)	(1.1)	(1.1)
Other comprehensive income (loss), before tax	447.3	(580.9)	964.6	(373.8)
Income tax expense (benefit) related to items of other comprehensive income (loss)	154.4	(200.8)	332.4	(129.0)
Other comprehensive income (loss), after tax	292.9	(380.1)	632.2	(244.8)
Comprehensive income (loss)	$ 324.2	$ (306.1)	$ 684.0	$ (108.8)