Summary of Significant Accounting Policies (Recently Adopted Changes in Accounting Principles) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Jan. 02, 2012	Dec. 31, 2011
Accounting Policies [Abstract]
Deferred acquisition costs	$ 211.3		$ 211.3		$ 5.6	$ 187.0
Deferred policy acquisition costs, amortization expense	$ 0.9	$ 1.4	$ 5.3	$ 5.7