CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (unaudited) - USD ($) $ in Thousands		Preferred Stock, Class A	Preferred Stock, Class B	Common Stock	Additional Paid-in Capital	Retained Earnings	AOCI (Loss), Net	Total
Balance at Dec. 31, 2016		$ 0	$ 3	$ 45	$ 96,116	$ 13,492	$ (165)	$ 109,491
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock issued, net of forfeiture					(7)			(7)
Employee and non-employee stock-based compensation expense					203			203
Net income						5,201		5,201
Other comprehensive loss							92	92
Balance at Jun. 30, 2017		0	3	45	96,312	18,693	(73)	114,980
Balance at Dec. 31, 2017		0	3	81	211,145	25,861	(206)	236,884
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock issued, net of forfeiture					440			440
Redemption of common stock for exercise of stock options and tax withholdings for restricted stock vesting					(72)			(72)
Employee and non-employee stock-based compensation expense					619			619
Issuance of common stock	[1]				(33)			(33)
Net income						12,156		12,156
Other comprehensive loss							(411)	(411)
Balance at Jun. 30, 2018		$ 0	$ 3	$ 81	$ 212,100	$ 38,017	$ (617)	$ 249,584

[1] Represents costs incurred in connection with the Company's initial public offering completed in the prior period.