Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (11.1)	$ (5.9)	$ 40.7	$ 130.1
Other comprehensive income (loss), before tax:
Unrealized gains/losses on securities	37.5	(44.9)	1,002.4	(419.3)
Other-than-temporary impairments	0.4	0.6	1.2	2.3
Pension and other post-employment benefit liability	(0.5)	(0.6)	(1.6)	(1.7)
Other comprehensive income (loss), before tax	37.4	(44.9)	1,002.0	(418.7)
Income tax expense (benefit) related to items of other comprehensive income (loss)	16.1	(15.4)	348.5	(144.4)
Other comprehensive income (loss), after tax	21.3	(29.5)	653.5	(274.3)
Comprehensive income (loss)	$ 10.2	$ (35.4)	$ 694.2	$ (144.2)