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		9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2014 Variable Annuity GMDB	Sep. 30, 2013 Variable Annuity GMDB	Sep. 30, 2014 Variable Annuity GMDB	Dec. 31, 2013 Variable Annuity GMDB	Sep. 30, 2014 Variable Annuity GMIB	Sep. 30, 2013 Variable Annuity GMIB	Sep. 30, 2014 Variable Annuity GMIB	Dec. 31, 2013 Variable Annuity GMIB	Sep. 30, 2014 Fixed Indexed Annuity GMWB & GMDB	Sep. 30, 2013 Fixed Indexed Annuity GMWB & GMDB	Sep. 30, 2014 Fixed Indexed Annuity GMWB & GMDB	Sep. 30, 2013 Fixed Indexed Annuity GMWB & GMDB	Sep. 30, 2014 Universal Life Secondary Guarantees	Sep. 30, 2013 Universal Life Secondary Guarantees	Sep. 30, 2014 Universal Life Secondary Guarantees	Sep. 30, 2013 Universal Life Secondary Guarantees	Sep. 30, 2014 Universal Life	Sep. 30, 2013 Universal Life	Sep. 30, 2014 Universal Life	Sep. 30, 2013 Universal Life
Movement in Guaranteed Benefit Liability, Gross [Roll Forward]
Balance, beginning of period	$ 14.4	$ 10.4	$ 17.0	$ 10.8	$ 5.5	$ 20.8	$ 9.5	$ 20.9	$ 141.2	$ 89.4	$ 90.0	$ 103.6	$ 164.1	$ 131.6	$ 153.2	$ 115.8
Incurred	1.5	0.6	(0.1)	1.8	0.5	(2.2)	(3.4)	(2.2)	10.5	12.1	26.8	44.9	8.1	9.1	20.7	31.9
Paid	(1.6)	(0.8)	(2.6)	(2.4)	0	0	0	0	(0.1)	0	(0.3)	(0.2)	(2.1)	(6.5)	(5.3)	(11.8)
Change due to net unrealized gains or losses included in AOCI	0	0	0	0	0	0	(0.1)	(0.1)	(6.1)	(0.9)	29.0	(47.7)					(0.2)	(0.1)	1.3	(1.8)
Assumption unlocking	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Balance, end of period	$ 14.3	$ 10.2	$ 14.3	$ 17.0	$ 6.0	$ 18.6	$ 6.0	$ 9.5	$ 145.5	$ 100.6	$ 145.5	$ 100.6	$ 169.9	$ 134.1	$ 169.9	$ 134.1