Separate Accounts, Death Benefits and Other Insurance Benefit Features and Embedded Product Derivatives Changes in Guaranteed Liability Balances (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Variable Annuity GMDB
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Liability balance, beginning of the period	$ 17.0	$ 10.8	$ 10.8
Incurred	2.1	2.0	1.0
Paid	(3.0)	(2.7)	(1.0)
Change due to net unrealized gains or losses included in AOCI	0	0	0
Assumption unlocking	0.2	6.9	0
Liability balance, end of the period	16.3	17.0	10.8
Variable Annuity GMIB
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Liability balance, beginning of the period	9.5	20.9	17.0
Incurred	2.0	(3.4)	3.8
Paid	(0.2)	0	0
Change due to net unrealized gains or losses included in AOCI	(0.1)	(0.1)	0.3
Assumption unlocking	5.2	(7.9)	0.2
Liability balance, end of the period	16.4	9.5	20.9
Fixed Indexed Annuity GMWB & GMDB
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Liability balance, beginning of the period	85.4	102.1	5.6
Incurred	33.4	60.8	37.2
Paid	(0.3)	(0.3)	0
Change due to net unrealized gains or losses included in AOCI	35.9	(58.5)	59.3
Assumption unlocking	7.4	18.7	0
Liability balance, end of the period	147.0	85.4	102.1
Universal Life
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Liability balance, beginning of the period	145.8	118.0	98.5
Incurred	35.0	33.6	21.1
Paid	(14.8)	(14.3)	(9.5)
Change due to net unrealized gains or losses included in AOCI	2.1	(2.1)	2.1
Assumption unlocking	(1.8)	10.6	5.8
Liability balance, end of the period	$ 166.3	$ 145.8	$ 118.0