Investments (Troubled Debt Restructurings on Financing Receivables) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) NumberOfLoans	Sep. 30, 2014 USD ($) NumberOfLoans	Sep. 30, 2015 USD ($) NumberOfLoans	Sep. 30, 2014 USD ($) NumberOfLoans
Financing Receivable, Modifications [Line Items]
Number of Loans | NumberOfLoans	0	35	5	39
Pre-Restructuring Recorded Investment	$ 0.0	$ 28.6	$ 2.6	$ 33.8
Post-Restructuring Recorded Investment	$ 0.0	$ 26.0	$ 2.7	$ 31.3
Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | NumberOfLoans	0	33	3	34
Pre-Restructuring Recorded Investment	$ 0.0	$ 27.5	$ 1.5	$ 28.3
Post-Restructuring Recorded Investment	$ 0.0	$ 24.9	$ 1.5	$ 25.6
Office [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | NumberOfLoans	0	1	2	1
Pre-Restructuring Recorded Investment	$ 0.0	$ 0.7	$ 1.1	$ 0.7
Post-Restructuring Recorded Investment	$ 0.0	$ 0.7	$ 1.2	$ 0.7
Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | NumberOfLoans	0	1	0	3
Pre-Restructuring Recorded Investment	$ 0.0	$ 0.4	$ 0.0	$ 2.1
Post-Restructuring Recorded Investment	$ 0.0	$ 0.4	$ 0.0	$ 2.3
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | NumberOfLoans	0	0	0	1
Pre-Restructuring Recorded Investment	$ 0.0	$ 0.0	$ 0.0	$ 2.7
Post-Restructuring Recorded Investment	$ 0.0	$ 0.0	$ 0.0	$ 2.7