Condensed Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Accumulated Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2015						$ 2,587
Comprehensive income	$ 46,618
Ending Balance at Jun. 30, 2016						8,309
Beginning Balance at Mar. 31, 2016						5,380
Comprehensive income	19,568
Ending Balance at Jun. 30, 2016						8,309
Beginning Balance at Dec. 31, 2016	$ 456,150	$ 204	$ 208,390	$ (22,370)	$ 270,418	(492)
Beginning Balance, Shares at Dec. 31, 2016	20,488,385	20,488,385
Treasury Stock Beginning Balance, Shares at Dec. 31, 2016	(1,258,250)			(1,258,250)
Comprehensive income	$ 31,913				29,005	2,908
Restricted common stock issued	396		396
Restricted common stock issued, Shares		13,888
Share-based compensation	628		628
Dividends to shareholders	(7,695)				(7,695)
Ending Balance at Jun. 30, 2017	$ 481,392	$ 204	209,414	$ (22,370)	291,728	2,416
Ending Balance, Shares at Jun. 30, 2017	20,502,273	20,502,273
Treasury Stock Ending Balance, Shares at Jun. 30, 2017	(1,258,250)			(1,258,250)
Beginning Balance at Mar. 31, 2017						460
Comprehensive income	$ 17,437
Ending Balance at Jun. 30, 2017	$ 481,392	$ 204	$ 209,414	$ (22,370)	$ 291,728	$ 2,416
Ending Balance, Shares at Jun. 30, 2017	20,502,273	20,502,273
Treasury Stock Ending Balance, Shares at Jun. 30, 2017	(1,258,250)			(1,258,250)