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	$ 51,425	0	0	0	51,425	0	51,425
Foreign currency translation adjustment	268	0	0	0	0	268	268
Reclassification of net (losses) gains on derivative instruments from OCI to net income, net of tax	$ (89)	$ 0	0	$ 0	0	(89)	(89)
Stock based compensation, shares		161		38
Stock based compensation, value		$ 0	1,338	$ (2,085)	0	0	(747)
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	(22,376)	0	(22,376)
Dividends per share	$ 0.48
Balance, end of period at Mar. 31, 2015		$ 507	1,315,060	$ (94,643)	293,807	(8,587)	1,506,144
Balance, shares at Mar. 31, 2015		50,683		3,645
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	38,054	0	0	0	38,054	0	38,054
Foreign currency translation adjustment	(118)	0	0	0	0	(118)	(118)
Reclassification of net (losses) gains on derivative instruments from OCI to net income, net of tax	$ 37	$ 0	0	$ 0	0	37	37
Stock based compensation, shares		166		31
Stock based compensation, value		$ 0	2,853	$ (2,398)	0	0	455
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	(23,922)	0	(23,922)
Dividends per share	$ 0.50
Balance, end of period at Mar. 31, 2016	$ 1,614,671	$ 520	$ 1,379,133	$ (96,346)	$ 340,041	$ (8,677)	$ 1,614,671
Balance, shares at Mar. 31, 2016		51,955		3,648