CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY Statement (USD $) In Thousands, except Per Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Shareholders' Equity [Member]
Balance, beginning of period at Dec. 31, 2012		$ 408	$ 849,218	$ (90,702)	$ 172,791	$ 2,317	$ 934,032
Balance, shares at Dec. 31, 2012		40,792		3,571
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	67,890	0	0	0	67,890	0	67,890
Foreign currency translation	81	0	0	0	0	81	81
Reclassification of net gains on derivative instruments	(549)	0	0	0	0	(549)	(549)
Unrealized loss on cash flow hedging derivatives, net of tax	0
Stock based compensation, shares		165		32
Stock based compensation, value		0	2,809	(1,294)	0	0	1,515
Issuance of shares		1,103
Issuance of shares, value		13	44,215		0	0	44,415
Dividends on common stock		0	0	0	(43,102)	0	(43,102)
Issuance of shares, treasury stock				(6)
Issuance of shares, treasury stock, value				187
Dividends per share	$ 1.14
Balance, end of period at Sep. 30, 2013		421	896,242	(91,809)	197,579	1,849	1,004,282
Balance, shares at Sep. 30, 2013		42,060		3,597
Balance, beginning of period at Dec. 31, 2013	1,030,670	423	910,184	(91,744)	209,091	2,716	1,030,670
Balance, shares at Dec. 31, 2013		42,340		3,595
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	83,517	0	0	0	83,517	0	83,517
Foreign currency translation	155	0	0	0	0	155	155
Reclassification of net gains on derivative instruments	(549)	0	0	0	0	(549)	(549)
Unrealized loss on cash flow hedging derivatives, net of tax	(1,011)	0	0	0	0	(1,011)	(1,011)
Stock based compensation, shares		118		0
Stock based compensation, value		0	2,727	(922)	0	0	1,805
Issuance of shares		296
Issuance of shares, value		5	13,479		0	0	13,525
Dividends on common stock		0	0	0	(46,426)	0	(46,426)
Issuance of shares, treasury stock				15
Issuance of shares, treasury stock, value				41
Dividends per share	$ 1.20
Balance, end of period at Sep. 30, 2014	$ 1,081,686	$ 428	$ 926,390	$ (92,625)	$ 246,182	$ 1,311	$ 1,081,686
Balance, shares at Sep. 30, 2014		42,754		3,610