Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 54.0	$ 20.5
Other comprehensive income (loss), before tax:
Unrealized gains/losses on securities	79.5	517.5
Other-than-temporary impairments	1.6	0.4
Pension and other post-employment benefit liability	(0.6)	(0.6)
Other comprehensive income (loss), before tax	80.5	517.3
Income tax expense (benefit) related to items of other comprehensive income (loss)	27.8	178.0
Other comprehensive income (loss), after tax	52.7	339.3
Comprehensive income (loss)	$ 106.7	$ 359.8