Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Stock	Additional paid-in capital	Retained earnings
Beginning balance, shares at Dec. 31, 2014		57,192,212
Beginning balance at Dec. 31, 2014	$ 1,326,911	$ 572	$ 1,227,091	$ 99,248
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, shares		23,954
Issuance of common stock, including stock option exercises	62	$ 0	62
Dividends on common stock	(67,507)			(67,507)
Share-based compensation	93		93
Net (loss) income	25,516			25,516
Ending balance, shares at Jun. 30, 2015		57,216,166
Ending balance at Jun. 30, 2015	1,285,075	$ 572	1,227,246	57,257
Beginning balance, shares at Dec. 31, 2014		57,192,212
Beginning balance at Dec. 31, 2014	1,326,911	$ 572	1,227,091	99,248
Increase (Decrease) in Stockholders' Equity
Dividends on common stock	$ (103,900)
Ending balance, shares at Dec. 31, 2015	55,581,005	55,581,005
Ending balance at Dec. 31, 2015	$ 1,152,357	$ 556	1,202,418	(50,617)
Beginning balance, shares at Jun. 30, 2015		57,216,166
Beginning balance at Jun. 30, 2015	$ 1,285,075	$ 572	1,227,246	57,257
Ending balance, shares at Dec. 31, 2015	55,581,005	55,581,005
Ending balance at Dec. 31, 2015	$ 1,152,357	$ 556	1,202,418	(50,617)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, shares		18,707
Issuance of common stock, including stock option exercises	30	$ 0	30
Repurchased of common stock		(1,134,528)
Repurchases of common stock	(12,522)	$ (11)	(12,511)
Dividends on common stock	(24,648)			(24,648)
Share-based compensation	74		74
Net (loss) income	$ (109,186)			(109,186)
Ending balance, shares at Jun. 30, 2016	54,465,184	54,465,184
Ending balance at Jun. 30, 2016	$ 1,006,105	$ 545	$ 1,190,011	$ (184,451)