CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock Class A Common Stock	Common Stock Class B Common Stock	Common Stock	Additional Paid In Capital. Class A Common Stock	Additional Paid In Capital.	Retained Earnings Class A Common Stock	Retained Earnings Class B Common Stock	Retained Earnings	Accumulated Other Comprehensive Income	Class A Common Stock	Class B Common Stock	Total
Balance at beginning of period at Dec. 31, 2015									$ 2,049
Increase (Decrease) in Stockholders' Equity
Net income												$ 26,075
Net change in accumulated other comprehensive income									1,266			1,266
Balance at end of period at Jun. 30, 2016									3,315
Balance at beginning of period at Dec. 31, 2015									2,049
Balance at end of period at Dec. 31, 2016			$ 4,906		$ 138,192			$ 460,621	687			604,406
Balance (in shares) at Dec. 31, 2016	18,615	2,245
Increase (Decrease) in Stockholders' Equity
Net income								30,088				30,088
Net change in accumulated other comprehensive income									865			865
Dividends declared Common Stock:
Dividends declared Common Stock						$ (7,986)	$ (876)			$ (7,986)	$ (876)
Stock options exercised, net of shares redeemed					33							33
Stock options exercised, net of shares redeemed (in shares)	2
Repurchase of Class A Common Stock	$ (2)			$ (107)		$ (435)				(544)
Repurchase of Class A Common Stock (in shares)	(13)
Conversion of Class B Common Stock to Class A Common Stock (in shares)	2	(2)
Net change in notes receivable on Class A Common Stock				154						154
Deferred director compensation expense - Class A Common Stock				$ 96						$ 96
Deferred director compensation expense - Class A Common Stock (in shares)	5
Stock based compensation expense - performance stock units					237							237
Stock based compensation - restricted stock					292							292
Stock based compensation - restricted stock (in shares)	7
Stock based compensation expense - stock options					126							126
Balance at end of period at Jun. 30, 2017			$ 4,904		$ 139,023			$ 481,412	$ 1,552			$ 626,891
Balance (in shares) at Jun. 30, 2017	18,618	2,243