Fair Value Measurements (Details 5) (Nonrecurring Fair Value Measurements, Fair value hierarchy Level 3, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Mortgage loans
Assets and liabilities measured at fair value on a nonrecurring basis
Fair value of assets measured on nonrecurring basis	$ 206.0	$ 250.7	$ 3.9
Net (gain) loss due to change in fair value of assets measured on nonrecurring basis	27.7	79.6	8.0
Mortgage servicing rights
Assets and liabilities measured at fair value on a nonrecurring basis
Fair value of assets measured on nonrecurring basis	4.4	1.0
Net (gain) loss due to change in fair value of assets measured on nonrecurring basis	1.1	0.6
Real estate
Assets and liabilities measured at fair value on a nonrecurring basis
Fair value of assets measured on nonrecurring basis		1.4	0.9
Net (gain) loss due to change in fair value of assets measured on nonrecurring basis		0.3	0.8
Customer-based intangible asset
Assets and liabilities measured at fair value on a nonrecurring basis
Fair value of assets measured on nonrecurring basis			19.1
Long-term debt obligation
Assets and liabilities measured at fair value on a nonrecurring basis
Fair value of liabilities measured on nonrecurring basis			$ 19.1