Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Allowance for credit losses	$ 2,543		$ 2,545
Amounts pledged	657,527		546,334
Accumulated amortization	61,671		54,919
Accumulated allowance	8,062		8,444
Net accumulated depreciation	107,810		104,812
Unamortized debt issuance expense	890		1,132
Deferred tax assets, gross	$ 61,198		$ 63,481
Class A Stock [Member]
Common stock, shares authorized (in shares)	50,000,000		50,000,000
Common stock, shares issued (in shares)	13,259,715		13,238,486
Common stock, shares outstanding (in shares)	13,259,715	13,263,532	13,238,486	13,650,149	13,634,831	13,530,688
Common stock, par value (dollars per share)	$ 0.001		$ 0.001
Class B Stock [Member]
Common stock, shares authorized (in shares)	99,665		99,665
Common stock, shares issued (in shares)	99,665		99,665
Common stock, shares outstanding (in shares)	99,665		99,665
Common stock, par value (dollars per share)	$ 0.001		$ 0.001