Separate Accounts, Death Benefits and Other Insurance Benefit Features and Embedded Product Derivatives - Changes in Guaranteed Insurance Benefit Liability Balances (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Universal Life
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Balance, beginning of period	$ 308.4	$ 324.8	$ 273.4	$ 300.4
Incurred	(18.4)	(18.2)	(38.0)	(32.0)
Change due to net unrealized gains or losses included in AOCI	8.6	17.0	(6.8)	6.4
Assumption unlocking	0	0	0	0
Balance, end of period	318.2	326.0	318.2	326.0
Annuity GMDB
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Balance, beginning of period	16.6	10.6	17.0	10.8
Incurred	(1.5)	0.8	(1.6)	1.2
Paid	(0.7)	(0.9)	(1.0)	(1.6)
Change due to net unrealized gains or losses included in AOCI	0	(0.1)	0	0
Assumption unlocking	0	0	0	0
Balance, end of period	14.4	10.4	14.4	10.4
Annuity GMIB
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Balance, beginning of period	8.7	22.0	9.5	20.9
Incurred	(3.2)	(1.2)	(3.9)	0
Paid	0	0	0	0
Change due to net unrealized gains or losses included in AOCI	0	0	(0.1)	(0.1)
Assumption unlocking	0	0	0	0
Balance, end of period	5.5	20.8	5.5	20.8
Fixed Indexed Annuity GMWB & GMDB
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Balance, beginning of period	114.7	117.5	90.0	103.6
Incurred	(11.3)	(20.2)	(16.3)	(32.8)
Paid	(0.1)	(0.1)	(0.2)	(0.2)
Change due to net unrealized gains or losses included in AOCI	15.3	(48.2)	35.1	(46.8)
Assumption unlocking	0	0	0	0
Balance, end of period	141.2	89.4	141.2	89.4
Universal Life
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Balance, beginning of period	156.1	128.0	153.2	115.8
Incurred	(8.6)	(7.6)	(12.6)	(22.8)
Paid	(1.3)	(1.9)	(3.2)	(5.3)
Change due to net unrealized gains or losses included in AOCI	0.7	(2.1)	1.5	(1.7)
Assumption unlocking	0	0	0	0
Balance, end of period	$ 164.1	$ 131.6	$ 164.1	$ 131.6