STATEMENT OF CHANGES IN EQUITY - 6 months ended Jun. 30, 2017 - USD ($) $ in Thousands	Total	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Shares issued, beginning balance at Dec. 31, 2016	52,598,005	52,598,005
Equity, beginning balance at Dec. 31, 2016	$ 1,888,280	$ 526	$ 1,749,574	$ 161,021	$ (18,126)	$ (4,715)
Cumulative effect of accounting change	10,982	0	0	10,982	0	0
Net income	97,079	0	0	97,079	0	0
Other comprehensive income	258	0	0	0		258
Repurchase of common stock	(17,512)	$ 0	0	0	(17,512)	0
Common stock issued, shares		0
Common stock issued, value	(1,749)	$ 0	(15,961)	0	14,212	0
Common stock dividends - $0.84 per share	$ (44,042)	$ 0	470	(44,512)	0	0
Shares issued, ending balance at Jun. 30, 2017	52,598,005	52,598,005
Equity, ending balance at Jun. 30, 2017	$ 1,933,296	$ 526	$ 1,734,083	$ 224,570	$ (21,426)	$ (4,457)