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 [Member]
Beginning Balance at Dec. 31, 2015						$ 2,587
Comprehensive income	$ 27,050
Ending Balance at Mar. 31, 2016						5,380
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	$ 14,476				13,524	952
Share-based compensation	321		321
Dividends to shareholders	(3,846)				(3,846)
Ending Balance at Mar. 31, 2017	$ 467,101	$ 204	$ 208,711	$ (22,370)	$ 280,096	$ 460
Ending Balance, Shares at Mar. 31, 2017	20,488,385	20,488,385
Treasury Stock Ending Balance, Shares at Mar. 31, 2017	(1,258,250)			(1,258,250)