Notes and Loan Payable and Amounts Due Under Repurchase Agreements (Repurchase Agreements Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Repurchase agreement, maximum amount borrowed	$ 113.0	$ 40.6	$ 138.7
Repurchase agreement, average borrowings	$ 4.5	$ 0.5	$ 9.2
Repurchase agreement, weighted average interest rate	0.66%	0.39%	0.19%