Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for Unfunded Credit Reserves) (Details) - Allowance for Unfunded Credit Reserve - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for unfunded credit reserves
Beginning balance	$ 16,121	$ 20,360	$ 12,712
(Reversal of) provision for unfunded credit reserves	(2,803)	(4,239)	7,648
Ending balance	$ 13,318	$ 16,121	$ 20,360