Employee Benefit Plans - Stock Purchase Plan (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee benefit plans [Line Items]
Recorded in share-based compensation, after the effects of DAC	$ 9.0	$ 7.0	$ 7.0
Employee Stock [Member] | Employee Stock Purchase Plan [Member]
Employee benefit plans [Line Items]
Proceeds from purchase of shares by employees	0.9	0.9	0.6
Number of shares issued by the Company	43,273	57,980	54,612
Recorded in share-based compensation, after the effects of DAC	$ 0.2	$ 0.3	$ 0.2