Separate Accounts, Death Benefits and Other Insurance Benefit Features and Embedded Product Derivative - Changes in Guaranteed Insurance Benefit Liability Balances (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Annuity GMDB
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Balance, beginning of period	$ 17.0	$ 10.8
Incurred	(0.1)	0.4
Paid	(0.3)	(0.7)
Change due to net unrealized gains or losses included in AOCI	0	0.1
Assumption unlocking	0	0
Liability balance, end of the period	16.6	10.6
Annuity GMIB
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Balance, beginning of period	9.5	20.9
Incurred	(0.7)	1.2
Paid	0	0
Change due to net unrealized gains or losses included in AOCI	(0.1)	(0.1)
Assumption unlocking	0	0
Liability balance, end of the period	8.7	22.0
Fixed Indexed Annuity GMWB & GMDB
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Balance, beginning of period	90.0	103.6
Incurred	5.0	12.6
Paid	(0.1)	(0.1)
Change due to net unrealized gains or losses included in AOCI	(19.8)	(1.4)
Assumption unlocking	0	0
Liability balance, end of the period	114.7	117.5
Universal Life Secondary Guarantees
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Balance, beginning of period	153.2	115.8
Incurred	4.0	15.2
Paid	(1.9)	(3.4)
Assumption unlocking	0	0
Liability balance, end of the period	156.1	128.0
Universal Life
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Change due to net unrealized gains or losses included in AOCI	(0.8)	(0.4)
Universal Life
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Additional liability balance, beginning of the period	273.4	300.4
Expense	19.6	13.8
Change due to net unrealized gains or losses included in AOCI	15.4	10.6
Assumption unlocking	0	0
Additional liability balance, end of the period	$ 308.4	$ 324.8