Borrowings - Obligations Under Capital Lease (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Obligations Under Capital Lease
Average balance	$ 11,615	$ 25,507	$ 15,187	$ 25,573
Weighted average interest rate	4.09%	3.25%	3.87%	3.01%
Total interest expense	$ 122	$ 205	$ 444	$ 585
Unpaid principal balance	$ 9,630		$ 9,630		$ 20,971
Weighted average interest rate	4.16%		4.16%		3.26%
Furniture, fixtures, equipment and building improvements pledged to creditors	$ 19,022		$ 19,022		$ 23,915
Capitalized software pledged to creditors	1,231		1,231		$ 1,568
Maximum
Obligations Under Capital Lease
Maximum daily amount outstanding	$ 13,032	$ 26,641	$ 20,971	$ 30,044