Bank Call Loans - Summary of Bank Call Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Bank Call Loans [Abstract]
Year-end balance	$ 145,800	$ 100,200
Weighted interest rate (at end of year)	1.77%	1.56%
Maximum balance (at any month-end)	$ 151,900	$ 189,000
Average amount outstanding (during the year)	$ 106,455	$ 116,267
Average interest rate (during the year)	1.52%	1.28%