Condensed Consolidated Statements of Changes in Shareholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit
Dividends paid per common share (in dollars per share)	$ 0.63
Beginning Balance at Dec. 31, 2017	$ 2,458,247	$ 2,127	$ 3,933,829	$ (1,477,709)
Beginning Balance (in shares) at Dec. 31, 2017		212,717,549
Increase (Decrease) in Shareholders' Equity
Stock option activity	5,244	$ 3	5,241
Stock option activity (in shares)		297,605
Restricted stock activity	(8,288)	$ 5	(8,293)
Restricted stock activity (in shares)		483,095
Dividends paid	(134,717)			(134,717)
Net income	96,772			96,772
Ending Balance at Mar. 31, 2018	2,416,848	$ 2,135	3,930,777	(1,516,064)
Ending Balance (in shares) at Mar. 31, 2018		213,498,249
Beginning Balance at Dec. 31, 2017	2,458,247	$ 2,127	3,933,829	(1,477,709)
Beginning Balance (in shares) at Dec. 31, 2017		212,717,549
Increase (Decrease) in Shareholders' Equity
Net income	188,770
Ending Balance at Jun. 30, 2018	$ 2,378,768	$ 2,137	3,935,517	(1,558,886)
Ending Balance (in shares) at Jun. 30, 2018		213,737,939
Dividends paid per common share (in dollars per share)	$ 0.63
Beginning Balance at Mar. 31, 2018	$ 2,416,848	$ 2,135	3,930,777	(1,516,064)
Beginning Balance (in shares) at Mar. 31, 2018		213,498,249
Increase (Decrease) in Shareholders' Equity
Stock option activity	4,127	$ 2	4,125
Stock option activity (in shares)		236,240
Restricted stock activity	615	$ 0	615
Restricted stock activity (in shares)		3,450
Dividends paid	(134,820)			(134,820)
Net income	91,998			91,998
Ending Balance at Jun. 30, 2018	$ 2,378,768	$ 2,137	3,935,517	(1,558,886)
Ending Balance (in shares) at Jun. 30, 2018		213,737,939
Dividends paid per common share (in dollars per share)	$ 0.68
Beginning Balance at Dec. 31, 2018	$ 2,265,607	$ 2,142	3,952,503	(1,689,038)
Beginning Balance (in shares) at Dec. 31, 2018	214,211,932	214,211,932
Increase (Decrease) in Shareholders' Equity
Stock option activity	$ 592	$ 0	592
Stock option activity (in shares)		26,799
Restricted stock activity	(5,323)	$ 4	(5,327)
Restricted stock activity (in shares)		406,769
Dividends paid	(146,202)			(146,202)
Net income	93,010			93,010
Ending Balance at Mar. 31, 2019	2,207,684	$ 2,146	3,947,768	(1,742,230)
Ending Balance (in shares) at Mar. 31, 2019		214,645,500
Beginning Balance at Dec. 31, 2018	$ 2,265,607	$ 2,142	3,952,503	(1,689,038)
Beginning Balance (in shares) at Dec. 31, 2018	214,211,932	214,211,932
Increase (Decrease) in Shareholders' Equity
Net income	$ 186,043
Ending Balance at Jun. 30, 2019	$ 2,158,687	$ 2,147	3,951,949	(1,795,409)
Ending Balance (in shares) at Jun. 30, 2019	214,673,135	214,673,135
Dividends paid per common share (in dollars per share)	$ 0.68
Beginning Balance at Mar. 31, 2019	$ 2,207,684	$ 2,146	3,947,768	(1,742,230)
Beginning Balance (in shares) at Mar. 31, 2019		214,645,500
Increase (Decrease) in Shareholders' Equity
Restricted stock activity	4,182	$ 1	4,181
Restricted stock activity (in shares)		27,635
Dividends paid	(146,212)			(146,212)
Net income	93,033
Ending Balance at Jun. 30, 2019	$ 2,158,687	$ 2,147	$ 3,951,949	$ (1,795,409)
Ending Balance (in shares) at Jun. 30, 2019	214,673,135	214,673,135