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]
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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	39,867	0	0	0	39,867	0
Foreign currency translation adjustment	(118)	0	0	0	0	(118)
Reclassification of net losses on derivative instruments from OCI to net income, net of tax	37	$ 0	0	$ 0	0	37
Stock based compensation, shares		166		31
Stock based compensation, value	455	$ 0	2,853	$ (2,398)	0	0
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	$ (23,922)	0	0	0	(23,922)	0
Dividends per share	$ 0.50
Balance, end of period at Mar. 31, 2016	$ 1,619,087	$ 520	1,379,133	$ (96,346)	344,457	(8,677)
Balance, shares at Mar. 31, 2016		51,955		3,648
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption	2,603	$ 0	0	$ 0	2,603	0
Balance, shares at Dec. 31, 2016		51,958		3,626
Balance, beginning of period at Dec. 31, 2016	1,676,227	$ 520	1,384,271	$ (95,769)	396,919	(9,714)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	56,567	0	0	0	56,567	0
Foreign currency translation adjustment	51	0	0	0	0	51
Reclassification of net losses on derivative instruments from OCI to net income, net of tax	93	$ 0	0	$ 0	0	93
Stock based compensation, shares		127		15
Stock based compensation, value	1,459	$ 1	2,929	$ (1,471)	0	0
Dividends on common stock	$ (25,194)	0	0	0	(25,194)	0
Dividends per share	$ 0.525
Balance, end of period at Mar. 31, 2017	$ 1,709,203	$ 521	$ 1,387,200	$ (97,240)	$ 428,292	$ (9,570)
Balance, shares at Mar. 31, 2017		52,085		3,641