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	$ 82,398	0	0	0	82,398	0	82,398
Foreign currency translation adjustment	212	0	0	0	0	212	212
Reclassification of net (losses) gains on derivative instruments from OCI to net income, net of tax	$ (180)	$ 0	0	$ 0	0	(180)	(180)
Stock based compensation, shares		164		17
Stock based compensation, value		$ 0	2,888	$ (1,567)	0	0	1,321
Issuance of shares		0
Issuance of shares, value		$ 2			0	0
Adjustments to additional paid in capital, stock issued, issuance costs			(122)
Stock issued, value, net of fees							(120)
Issuance of shares, treasury stock				0
Issuance of shares, treasury stock, value				$ 0
Dividends on common stock		0	0	0	(44,760)	0	(44,760)
Dividends per share	$ 0.96
Balance, end of period at Jun. 30, 2015		$ 507	1,316,610	$ (94,125)	302,396	(8,734)	1,516,654
Balance, shares at Jun. 30, 2015		50,686		3,624
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	73,623	0	0	0	73,623	0	73,623
Foreign currency translation adjustment	(110)	0	0	0	0	(110)	(110)
Reclassification of net (losses) gains on derivative instruments from OCI to net income, net of tax	$ 74	$ 0	0	$ 0	0	74	74
Stock based compensation, shares		167		28
Stock based compensation, value		$ 0	4,065	$ (2,317)	0	0	1,748
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				$ 0
Dividends on common stock		0	0	0	(47,865)	0	(47,865)
Dividends per share	$ 1.00
Balance, end of period at Jun. 30, 2016	$ 1,627,635	$ 520	$ 1,380,345	$ (96,265)	$ 351,667	$ (8,632)	$ 1,627,635
Balance, shares at Jun. 30, 2016		51,956		3,645