Income Tax Matters, Income Tax Benefit (Provision) Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Federal income tax (expense) benefit
Current federal tax (expense) benefit	$ 2.7	$ 0.7	$ (1.0)
Deferred federal income tax (expense) benefit	(47.8)	93.2	6.4
Federal benefit (expense) applied to increase (decrease) Additional capital/Other comprehensive income	(3.2)	33.5	(41.6)
Federal income tax (expense) benefit	(48.3)	127.4	(36.2)
Foreign income tax (expense) benefit
Current foreign tax (expense) benefit	0.6	2.1	1.0
Deferred foreign income tax (expense) benefit	(1.2)	(1.2)	0.3
Foreign benefit (expense) applied to increase (decrease) Additional capital/Other comprehensive income	(0.1)	0.4	(0.5)
Foreign income tax (expense) benefit	(0.7)	1.3	0.8
State income tax (expense) benefit
Current state tax (expense) benefit	(1.5)	0.4	(0.6)
Deferred state income tax (expense) benefit	(4.7)	1.8	5.1
State benefit (expense) applied to increase (decrease) additional capital/Other comprehensive income	(0.3)	4.3	(4.4)
State income tax (expense) benefit	(6.5)	6.5	0.1
Total income tax (expense) benefit
Current income tax (expense) benefit	1.8	3.2	(0.6)
Deferred income tax (expense) benefit	(53.7)	93.8	11.8
Benefit (expense) applied to increase (decrease) Additional capital/Other comprehensive income	(3.6)	38.2	(46.5)
Income tax (provision) benefit	$ (55.5)	$ 135.2	$ (35.3)