Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings (Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Cumulative effective adjustment from adoption of ASU			$ (1,410)		$ (1,410)
Balance at beginning of period at Dec. 31, 2018	$ 790	$ 1,262,063	(909,186)	$ 0	353,667
Balance (in shares) at Dec. 31, 2018	79,044,000
Net income			321,152		321,152
Total other comprehensive loss					0
Issuance of common stock under employee benefit plans, net of forfeitures and shares withheld to cover taxes		3,772			3,772
Issuance of common stock under employee benefit plans, net of forfeitures and shares withheld to cover taxes, shares	12,000
Net issuance of common stock upon exercise of stock options	$ 2	11,953			11,955
Net issuance of common stock upon exercise of stock options, shares	133,000
Share-based compensation		5,085			5,085
Share repurchases, including fees	$ (9)	(14,841)	(307,006)		$ (321,856)
Share repurchases, including fees, shares	(927,000)				(927,000)
Balance at end of period at Mar. 31, 2019	$ 783	1,268,032	(896,450)	0	$ 372,365
Balance (in shares) at Mar. 31, 2019	78,262,000
Balance at beginning of period at Dec. 31, 2019	$ 756	1,280,760	(889,066)	4,890	$ 397,340	[1]
Balance (in shares) at Dec. 31, 2019	75,619,000				75,618,659
Net income			300,438		$ 300,438
Total other comprehensive loss				(30,646)	(30,646)
Issuance of common stock under employee benefit plans, net of forfeitures and shares withheld to cover taxes		4,104			4,104
Issuance of common stock under employee benefit plans, net of forfeitures and shares withheld to cover taxes, shares	12,000
Net issuance of common stock upon exercise of stock options	$ 1	6,135			6,136
Net issuance of common stock upon exercise of stock options, shares	52,000
Share-based compensation		5,524			5,524
Share repurchases, including fees	$ (15)	(25,273)	(548,764)		$ (574,052)
Share repurchases, including fees, shares	(1,484,000)				(1,484,000)
Balance at end of period at Mar. 31, 2020	$ 742	$ 1,271,250	$ (1,137,392)	$ (25,756)	$ 108,844
Balance (in shares) at Mar. 31, 2020	74,199,000				74,199,261

[1] The balance sheet at December 31, 2019, has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by United States generally accepted accounting principles for complete financial statements.