CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY Statement - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Balance, shares at Dec. 31, 2018		53,889	3,566
Balance, beginning of period at Dec. 31, 2018	$ 1,942,382	$ 539	$ (95,546)	$ 1,499,070	$ 548,253	$ (9,934)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	72,806	0	0	0	72,806	0
Foreign currency translation adjustment	63	0	0	0	0	63
Reclassification of net losses on derivative instruments from OCI to net income, net of tax	112	$ 0	$ 0	0	0	112
Stock based compensation, shares		86	25
Stock based compensation, value	760	$ 0	$ (1,646)	2,406	0	0
Issuance of shares		21
Issuance of shares, treasury stock			(35)
Issuance of shares, value	2,450	$ 1	$ 932	1,517	0	0
Dividends on common stock	$ (28,781)	0	0	0	(28,781)	0
Dividends per share	$ 0.575
Balance, end of period at Mar. 31, 2019	$ 1,989,792	$ 540	$ (96,260)	1,502,993	592,278	(9,759)
Balance, shares at Mar. 31, 2019		53,996	3,556
Balance, shares at Dec. 31, 2019		53,999	3,547
Balance, beginning of period at Dec. 31, 2019	2,039,094	$ 541	$ (96,015)	1,508,970	635,246	(9,648)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	50,704	0	0	0	50,704	0
Foreign currency translation adjustment	101	0	0	0	0	101
Reclassification of net losses on derivative instruments from OCI to net income, net of tax	113	$ 0	$ 0	0	0	113
Stock based compensation, shares		146	35
Stock based compensation, value	290	$ 0	$ (2,741)	3,031	0	0
Issuance of shares		0
Issuance of shares, treasury stock			(4)
Issuance of shares, value	259	$ 0	$ 112	147	0	0
Dividends on common stock	$ (30,085)	0	0	0	(30,085)	0
Dividends per share	$ 0.60
Balance, end of period at Mar. 31, 2020	$ 2,060,476	$ 541	$ (98,644)	$ 1,512,148	$ 655,865	$ (9,434)
Balance, shares at Mar. 31, 2020		54,145	3,578