Consolidated Statements of Shareholders' Deficit - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in- Capital	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Retained Earnings
Beginning balance, (in shares) at Dec. 31, 2015		56,336,566
Beginning balance at Dec. 31, 2015	$ (395,899)	$ 951	$ 149,895	$ (8,778)	$ (1,052,864)	$ 514,897
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	106,712					106,712
Other comprehensive income	256			256
Share based payment activity (in shares)		732,735
Share based payment activity	27,557		9,150		18,407
Dividends declared	(46,708)	$ (46,700)				(46,708)
Treasury purchases (in shares)		(769,352)
Treasury purchases	(35,926)				(35,926)
Ending balance, (in shares) at Dec. 31, 2016		56,299,949
Ending balance at Dec. 31, 2016	(365,282)	$ 951	159,045	(8,522)	(1,070,383)	553,627
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	122,327					122,327
Other comprehensive income	3,823			3,823
Share based payment activity (in shares)		538,069
Share based payment activity	39,020		23,403		15,617
Dividends declared	(48,682)	$ (48,600)				(48,682)
Treasury purchases (in shares)		(158,050)
Treasury purchases	$ (9,807)				(9,807)
Ending balance, (in shares) at Dec. 31, 2017	56,679,968	56,679,968
Ending balance at Dec. 31, 2017	$ (258,601)	$ 951	182,448	(4,699)	(1,064,573)	627,272
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	216,355					216,355
Other comprehensive income	(747)			(747)
Share based payment activity (in shares)		918,397
Share based payment activity	56,349		30,722		25,627
Dividends declared	(48,449)					(48,449)
Treasury purchases (in shares)		(1,919,158)
Treasury purchases	$ (148,679)				(148,679)
Ending balance, (in shares) at Dec. 31, 2018	55,679,207	55,679,207
Ending balance at Dec. 31, 2018	$ (183,772)	$ 951	$ 213,170	$ (5,446)	$ (1,187,625)	$ 795,178