STATEMENT OF CHANGES IN EQUITY - 9 months ended Sep. 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	115,876	0	0	115,876	0	0
Other comprehensive income	386	0	0	0		386
Repurchase of common stock	(17,512)	$ 0	0	0	(17,512)	0
Common stock issued, shares		0
Common stock issued, value	(24)	$ 0	(14,634)	0	14,610	0
Common stock dividends - $1.26 per share	$ (65,996)	$ 0	698	(66,694)	0	0
Shares issued, ending balance at Sep. 30, 2017	52,598,005	52,598,005
Equity, ending balance at Sep. 30, 2017	$ 1,931,992	$ 526	$ 1,735,638	$ 221,185	$ (21,028)	$ (4,329)