Consolidated Statements of Changes in Shareholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Accumulated Earnings (Deficit)
Balance at Dec. 31, 2014	$ (176,290)	$ 1,130	$ 888,860	$ (1,066,280)
Balance (in shares) at Dec. 31, 2014		112,981,088
Increase (Decrease) in Shareholders' Equity
Stock option activity	34,646	$ 25	34,621
Stock option activity (in shares)		2,511,639
Restricted stock activity	11,740	$ 1	11,739
Restricted stock activity (in shares)		101,594
Dividends paid	(251,732)	$ 0	0	(251,732)
Dividends paid (in shares)		0
Net income	128,122			128,122
Balance at Dec. 31, 2015	(253,514)	$ 1,156	935,220	(1,189,890)
Balance (in shares) at Dec. 31, 2015		115,594,321
Increase (Decrease) in Shareholders' Equity
Issuance of common stock	2,694,800	$ 861	2,693,939
Issuance of common stock, shares		86,074,167
Stock option activity	115,475	$ 59	115,416
Stock option activity (in shares)		5,870,282
Restricted stock activity	16,155	$ 1	16,154
Restricted stock activity (in shares)		138,057
Dividends paid	(428,352)	$ 0	0	(428,352)
Dividends paid (in shares)		0
Net income	289,305			289,305
Balance at Dec. 31, 2016	$ 2,433,869	$ 2,077	3,760,729	(1,328,937)
Balance (in shares) at Dec. 31, 2016	207,676,827	207,676,827
Increase (Decrease) in Shareholders' Equity
Issuance of common stock	$ 139,414	$ 38	139,376
Issuance of common stock, shares		3,864,872
Stock option activity	21,003	$ 10	20,993
Stock option activity (in shares)		1,013,984
Restricted stock activity	12,733	$ 2	12,731
Restricted stock activity (in shares)		161,866
Dividends paid	(529,370)	$ 0	0	(529,370)
Dividends paid (in shares)		0
Net income	380,598			380,598
Balance at Dec. 31, 2017	$ 2,458,247	$ 2,127	$ 3,933,829	$ (1,477,709)
Balance (in shares) at Dec. 31, 2017	212,717,549	212,717,549