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 (in shares) at Dec. 31, 2016		41,919,801
Balance at Dec. 31, 2016	$ 430,482	$ 419	$ 765,042	$ (334,979)	$ 0
Increase (Decrease) in Stockholders' Equity
Vesting of restricted stock	981		981
Equity component of convertible senior unsecured notes	2,656		2,656
Treasury stock (in shares)		(125,722)
Treasury Stock	(1,232)				(1,232)
Net income (loss)	85,097			85,097
Dividends on common stock	(51,946)		84	(52,030)
Balance (in shares) at Dec. 31, 2017		41,794,079
Balance at Dec. 31, 2017	466,038	$ 419	768,763	(301,912)	(1,232)
Increase (Decrease) in Stockholders' Equity
Vesting of restricted stock	265		265
Treasury Stock (in shares)		125,722
Treasury Stock	1,445		213		1,232
Net income (loss)	26,409			26,409
Dividends on common stock	(55,655)		124	(55,779)
Proceeds from public offerings of common stock (in shares)		6,196,578
Net proceeds from public offerings of common stock	64,880	$ 62	64,818
Offering costs	$ (373)		(373)
Balance (in shares) at Dec. 31, 2018	48,116,379	48,116,379
Balance at Dec. 31, 2018	$ 503,009	$ 481	833,810	(331,282)	0
Increase (Decrease) in Stockholders' Equity
Vesting of restricted stock	564		564
Equity component of convertible senior unsecured notes	2,445		2,445
Net income (loss)	70,699			70,699
Dividends on common stock	(64,540)		178	(64,718)
Proceeds from public offerings of common stock (in shares)		5,299,497
Net proceeds from public offerings of common stock	52,714	$ 53	52,661
Offering costs	(430)		(430)
Grants of restricted stock (in shares)		108,000
Grants of restricted stock	$ 0	$ 1	(1)
Balance (in shares) at Dec. 31, 2019	53,523,876	53,523,876
Balance at Dec. 31, 2019	$ 564,461	$ 535	$ 889,227	$ (325,301)	$ 0