CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY Statement - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Shareholders' Equity [Member]
Balance, shares at Dec. 31, 2014		50,522		3,607
Balance, beginning of period at Dec. 31, 2014		$ 505	$ 1,313,844	$ (92,558)	$ 264,758	$ (8,766)	$ 1,477,783
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	$ 106,196	0	0	0	106,196	0	106,196
Foreign currency translation adjustment	445	0	0	0	0	445	445
Reclassification of net (losses) gains on derivative instruments from OCI to net income, net of tax	$ (735)	$ 0	0	$ 0	0	(735)	(735)
Stock based compensation, shares		166		0
Stock based compensation, value		$ 0	3,304	$ (1,926)	0	0	1,378
Issuance of shares		0
Issuance of shares, value		$ 2			0	0
Adjustments to additional paid in capital, stock issued, issuance costs			469
Stock issued, value, net of fees							924
Issuance of shares, treasury stock				13
Issuance of shares, treasury stock, value				$ 453
Dividends on common stock		0	0	0	(67,145)	0	(67,145)
Dividends per share	$ 1.44
Balance, end of period at Sep. 30, 2015		$ 507	1,317,617	$ (94,031)	303,809	(9,056)	1,518,846
Balance, shares at Sep. 30, 2015		50,688		3,620
Balance, shares at Dec. 31, 2015		51,789		3,617
Balance, beginning of period at Dec. 31, 2015	$ 1,600,174	$ 518	1,376,291	$ (93,948)	325,909	(8,596)	1,600,174
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	118,228	0	0	0	118,228	0	118,228
Foreign currency translation adjustment	(84)	0	0	0	0	(84)	(84)
Reclassification of net (losses) gains on derivative instruments from OCI to net income, net of tax	$ (1,432)	$ 0	0	$ 0	0	(1,432)	(1,432)
Stock based compensation, shares		168		13
Stock based compensation, value		$ 0	5,650	$ (1,904)	0	0	3,746
Issuance of shares		0
Issuance of shares, value		$ 2			0	0
Adjustments to additional paid in capital, stock issued, issuance costs			(11)
Stock issued, value, net of fees							(9)
Issuance of shares, treasury stock				0
Issuance of shares, treasury stock, value
Dividends on common stock		0	0	0	(71,816)	0	(71,816)
Dividends per share	$ 1.50
Balance, end of period at Sep. 30, 2016	$ 1,648,807	$ 520	$ 1,381,930	$ (95,852)	$ 372,321	$ (10,112)	$ 1,648,807
Balance, shares at Sep. 30, 2016		51,957		3,630