Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Allowance for credit losses	$ 2,503		$ 2,545
Amounts pledged	799,379		546,334
Accumulated amortization	64,763		54,919
Accumulated allowance	8,037		8,444
Net accumulated depreciation	109,278		104,812
Unamortized debt issuance expense	769		1,132
Deferred tax assets, gross	$ 62,014		$ 63,481
Class A Stock [Member]
Common stock, shares authorized (in shares)	50,000,000		50,000,000
Common stock, shares issued (in shares)	13,268,439		13,238,486
Common stock, shares outstanding (in shares)	13,268,439	13,259,715	13,238,486	13,333,368	13,650,149	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