Fair Value Measurements (Details 5) (Nonrecurring Fair Value Measurements, Fair value hierarchy Level 3, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Mortgage loans
Assets and liabilities measured at fair value on a nonrecurring basis
Fair value of assets measured on nonrecurring basis	$ 63.8	$ 101.6	$ 63.8	$ 101.6
Net (gain) loss due to change in fair value of assets measured on nonrecurring basis	9.7	4.6	9.1	22.3
Mortgage loans | Minimum
Assets and liabilities measured at fair value on a nonrecurring basis
Discount rate (as a percent)			8.80%	8.00%
Terminal capitalization rate (as a percent)			7.30%	7.50%
Average market rent growth rate (as a percent)			2.50%	1.00%
Mortgage loans | Maximum
Assets and liabilities measured at fair value on a nonrecurring basis
Discount rate (as a percent)			11.00%	20.00%
Terminal capitalization rate (as a percent)			9.00%	10.50%
Average market rent growth rate (as a percent)			10.90%	10.90%
Mortgage servicing rights
Assets and liabilities measured at fair value on a nonrecurring basis
Fair value of assets measured on nonrecurring basis		7.6		7.6
Net (gain) loss due to change in fair value of assets measured on nonrecurring basis		$ 0		$ (1.3)
Mortgage servicing rights | Input
Assets and liabilities measured at fair value on a nonrecurring basis
Discount rate (as a percent)				3.90%