CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member] Cumulative Effect, Period of Adoption, as Adjusted	Common Stock [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings [Member] Cumulative Effect, Period of Adoption, as Adjusted	Retained Earnings [Member]	Treasury Stock [Member] Cumulative Effect, Period of Adoption, as Adjusted	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Cumulative Effect, Period of Adoption, as Adjusted	Accumulated Other Comprehensive Income (Loss) [Member]	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, as Adjusted	Total
Increase (Decrease) in Stockholders' Equity
Change in accounting principle and other			$ (13,141)							$ (13,141)
Balance at Dec. 31, 2018	$ 690,910	$ 690,910		$ 1,763,444	$ 1,776,585	$ (503,182)	$ (503,182)	$ (32)	$ (32)		$ 1,951,140	$ 1,964,281
Balance (in shares) at Dec. 31, 2018	81,239,000	81,239,000				(29,851,000)	(29,851,000)
Increase (Decrease) in Stockholders' Equity
Net income (loss)					340,099							340,099
Net unrealized appreciation on marketable securities, net of tax									$ 32			32
Exercise of common stock options and vested employee stock awards		$ 3,106										$ 3,106
Exercise of common stock options and vested employee stock awards (in shares)		707,000										232,514
Employee income tax paid on vested equity awards							$ (9,313)					$ (9,313)
Employee income tax paid on vested equity awards (in shares)							(173,000)
Sale of common stock under employee stock purchase plan		$ 3,165										3,165
Sale of common stock under employee stock purchase plan (in shares)		65,000
Stock based compensation expense		$ 5,770										5,770
Common stock purchased and cancelled		$ (16,145)										(16,145)
Common stock purchased and cancelled (in shares)		(268,000)
Treasury stock purchases							$ (78,476)					(78,476)
Treasury stock purchases (in shares)							(1,396,000)
Cash dividends declared					(24,364)							(24,364)
Balance at Dec. 31, 2019	$ 686,806	$ 686,806		$ 2,067,540	2,079,179	$ (590,971)	$ (590,971)				$ 2,163,375	2,175,014
Balance (in shares) at Dec. 31, 2019	81,743,000	81,743,000				(31,420,000)	(31,420,000)
Increase (Decrease) in Stockholders' Equity
Change in accounting principle and other			$ (11,639)							$ (11,639)
Net income (loss)					(8,515)							(8,515)
Exercise of common stock options and vested employee stock awards		$ 38										$ 38
Exercise of common stock options and vested employee stock awards (in shares)		287,000										2,578
Employee income tax paid on vested equity awards							$ (6,165)					$ (6,165)
Employee income tax paid on vested equity awards (in shares)							(108,000)
Sale of common stock under employee stock purchase plan		$ 2,781										2,781
Sale of common stock under employee stock purchase plan (in shares)		65,000
Stock based compensation expense		$ 6,802										6,802
Treasury stock purchases							$ (20,000)					(20,000)
Treasury stock purchases (in shares)							(386,000)
Cash dividends declared					(7,019)							(7,019)
Warrants issued to U.S. Treasury		8,248										8,248
Balance at Dec. 31, 2020		$ 704,675			2,052,006		$ (617,136)					2,139,545
Balance (in shares) at Dec. 31, 2020		82,095,000					(31,914,000)
Increase (Decrease) in Stockholders' Equity
Net income (loss)					111,910							111,910
Exercise of common stock options and vested employee stock awards		$ 606										$ 606
Exercise of common stock options and vested employee stock awards (in shares)		177,000										41,020
Employee income tax paid on vested equity awards							$ (1,576)					$ (1,576)
Employee income tax paid on vested equity awards (in shares)							(42,000)
Sale of common stock under employee stock purchase plan		$ 2,540										2,540
Sale of common stock under employee stock purchase plan (in shares)		64,000
Stock based compensation expense		$ 8,685										8,685
Warrants issued to U.S. Treasury		5,804										5,804
Balance at Dec. 31, 2021		$ 722,310			$ 2,163,916		$ (618,712)					$ 2,267,514
Balance (in shares) at Dec. 31, 2021		82,336,000					(31,956,000)