Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock Outstanding	Additional Paid-In Capital	Retained Earnings (Accumulated) Deficit	Treasury Stock
Balance at Dec. 31, 2014	$ 623,212	$ 417	$ 760,925	$ (138,130)
Balance (in shares) at Dec. 31, 2014		41,719,801
Increase (Decrease) in Stockholders' Equity
Grants of restricted stock	0	$ 2	(2)
Grants of restricted stock (in shares)		200,000
Vesting of restricted stock	2,301		2,301
Net income (loss)	(9,484)			(9,484)
Dividends on common stock	(104,381)		59	(104,440)
Balance at Dec. 31, 2015	511,648	$ 419	763,283	(252,054)
Balance (in shares) at Dec. 31, 2015		41,919,801
Increase (Decrease) in Stockholders' Equity
Vesting of restricted stock	1,699		1,699
Net income (loss)	(25,015)			(25,015)
Dividends on common stock	(57,850)		60	(57,910)
Balance at Dec. 31, 2016	$ 430,482	$ 419	765,042	(334,979)	$ 0
Balance (in shares) at Dec. 31, 2016	41,919,801	41,919,801
Increase (Decrease) in Stockholders' Equity
Vesting of restricted stock	$ 981		981
Net income (loss)	85,097			85,097
Dividends on common stock	(51,946)		84	(52,030)
Equity component of convertible senior unsecured notes	2,656		2,656
Treasury Stock	(1,232)				(1,232)
Treasury stock (in shares)		(125,722)
Balance at Dec. 31, 2017	$ 466,038	$ 419	$ 768,763	$ (301,912)	$ (1,232)
Balance (in shares) at Dec. 31, 2017	41,794,079	41,794,079