Notes Payable and Amounts Due Under Repurchase Agreements (Repurchase Agreements Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Notes Payable [Abstract]
Repurchase agreement, maximum amount borrowed	$ 138.7	$ 258.6	$ 0
Repurchase agreement, average borrowings	$ 9.2	$ 68.3
Repurchase agreement, weighted average interest rate	0.19%	0.20%