Reinsurance and Policy Provisions (Hannover Financing Arrangements) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Hannover Reinsurance Agreement, All Agreements [Member]
Ceded Credit Risk [Line Items]
Number of reinsurance agreements	2
2011 Hannover Reinsurance Agreement [Member]
Ceded Credit Risk [Line Items]
Net pretax statutory surplus benefit	$ 49.2
Statutory surplus benefit reduction, duration (years)	5 years
Reduction in pretax statutory surplus, current period	10.8	11.3	11.8
Reduction in pretax statutory surplus, due in one year	10.3
Reduction in pretax statutory surplus, due in two years	2.5
Risk charge rate	1.25%
Risk charges	0.8	1.3	1.8
2013 Hannover Reinsurance Agreement [Member]
Ceded Credit Risk [Line Items]
Risk charge rate	1.25%
Risk charges	15.7	7.0
Waived surrender charges on penalty free withdrawals and deaths on certain business, percentage	45.60%
Reserve credit	322.5	288.2
2005 Hannover Reinsurance Agreement [Member]
Ceded Credit Risk [Line Items]
Risk charges		5.4	9.9
Waived surrender charges on penalty free withdrawals and deaths on certain business, percentage	47.00%
2008 Hannover Reinsurance Agreement [Member]
Ceded Credit Risk [Line Items]
Net pretax statutory surplus benefit	29.5
Reduction in pretax statutory surplus, current period		6.9	6.8
Risk charge rate	1.25%
Risk charges		$ 0.1	$ 0.5