CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - UNAUDITED - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Adjustments due to adoption of new accounting standards	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Accumulated Earnings	Accumulated Earnings Adjustments due to adoption of new accounting standards	Noncontrolling Interest
Balance, beginning of period at Dec. 31, 2020	$ 422,395	$ 700	$ 470,557		$ (894,126)	$ (31,138)	$ 876,402		$ 0
Balance, beginning of period, shares at Dec. 31, 2020		32,713,000
Net income							19,631
Unrealized gain (loss) on short-term investments, net of tax						(6)
Foreign currency translation adjustments						(355)
Total comprehensive income (loss), net of tax	19,270
Repurchase of common stock	(11,721)	$ (1)	(5,202)		(6,518)
Repurchase of common stock, shares		(252,000)
Issuance of common stock pursuant to employee stock purchase plan	619		619
Issuance of common stock pursuant to employee stock purchase plan, shares		16,000
Issuance of restricted common stock pursuant to stock-based compensation plans		$ 5	(5)
Issuance of restricted common stock pursuant to stock-based compensation plans, shares		487,000
Cancellation of restricted common stock issued pursuant to stock-based compensation plans, shares		(1,000)
Stock-based compensation expense	5,395		5,395
Dividends	(8,243)						(8,243)
Balance, ending of period at Mar. 31, 2021	427,715	$ 704	471,364		(900,644)	(31,499)	887,790
Balance, ending of period, shares at Mar. 31, 2021		32,963,000
Balance, beginning of period at Dec. 31, 2020	422,395	$ 700	470,557		(894,126)	(31,138)	876,402		0
Balance, beginning of period, shares at Dec. 31, 2020		32,713,000
Net income	38,952
Unrealized gain (loss) on short-term investments, net of tax	(13)
Foreign currency translation adjustments	1,857
Total comprehensive income (loss), net of tax	40,796
Balance, ending of period at Jun. 30, 2021	439,780	$ 704	477,010		(907,601)	(29,294)	898,961		0
Balance, ending of period, shares at Jun. 30, 2021		32,797,000
Balance, beginning of period at Mar. 31, 2021	427,715	$ 704	471,364		(900,644)	(31,499)	887,790
Balance, beginning of period, shares at Mar. 31, 2021		32,963,000
Net income	19,321						19,321
Unrealized gain (loss) on short-term investments, net of tax	(7)					(7)
Foreign currency translation adjustments	2,212					2,212
Total comprehensive income (loss), net of tax	21,526
Repurchase of common stock	(7,049)		(92)		(6,957)
Repurchase of common stock, shares		(156,000)
Issuance of common stock pursuant to employee stock purchase plan	716		716
Issuance of common stock pursuant to employee stock purchase plan, shares		19,000
Issuance of restricted common stock pursuant to stock-based compensation plans, shares		6,000
Cancellation of restricted common stock issued pursuant to stock-based compensation plans, shares		(35,000)
Stock-based compensation expense	5,022		5,022
Dividends	(8,150)						(8,150)
Balance, ending of period at Jun. 30, 2021	439,780	$ 704	477,010		(907,601)	(29,294)	898,961		0
Balance, ending of period, shares at Jun. 30, 2021		32,797,000
Balance, beginning of period at Dec. 31, 2021	$ 440,244	$ 705	488,303	$ (9,802)	(930,106)	(38,353)	916,060	$ 9,802	3,635
Balance, beginning of period, shares at Dec. 31, 2021	32,495,000	32,495,000
Net income							6,113
Unrealized gain (loss) on short-term investments, net of tax						(2)
Foreign currency translation adjustments						(1,182)
Total comprehensive income (loss), net of tax	$ 4,929
Repurchase of common stock	(23,801)	$ (1)	(7,804)		(15,996)
Repurchase of common stock, shares		(389,000)
Issuance of common stock pursuant to employee stock purchase plan	650		650
Issuance of common stock pursuant to employee stock purchase plan, shares		12,000
Issuance of restricted common stock pursuant to stock-based compensation plans		$ 5	(5)
Issuance of restricted common stock pursuant to stock-based compensation plans, shares		476,000
Cancellation of restricted common stock issued pursuant to stock-based compensation plans, shares		(34,000)
Stock-based compensation expense	5,581		5,581
Settlement of convertible debt securities, net of tax	(4,845)		(4,845)
Dividends	(8,586)						(8,586)
Balance, ending of period at Mar. 31, 2022	414,172	$ 709	472,078		(946,102)	(39,537)	923,389		3,635
Balance, ending of period, shares at Mar. 31, 2022		32,560,000
Balance, beginning of period at Dec. 31, 2021	$ 440,244	$ 705	488,303	$ (9,802)	(930,106)	(38,353)	916,060	$ 9,802	3,635
Balance, beginning of period, shares at Dec. 31, 2021	32,495,000	32,495,000
Net income	$ 11,430
Unrealized gain (loss) on short-term investments, net of tax	3
Foreign currency translation adjustments	(17,182)
Total comprehensive income (loss), net of tax	(5,749)
Balance, ending of period at Jun. 30, 2022	$ 377,022	$ 709	479,271		(967,659)	(55,532)	920,233		0
Balance, ending of period, shares at Jun. 30, 2022	32,195,000	32,195,000
Balance, beginning of period at Mar. 31, 2022	$ 414,172	$ 709	472,078		(946,102)	(39,537)	923,389		3,635
Balance, beginning of period, shares at Mar. 31, 2022		32,560,000
Net income	5,317						(5,317)
Unrealized gain (loss) on short-term investments, net of tax	5					5
Foreign currency translation adjustments	(16,000)					(16,000)
Total comprehensive income (loss), net of tax	(10,678)
Repurchase of common stock	(21,673)		(116)		(21,557)
Repurchase of common stock, shares		(362,000)
Issuance of common stock pursuant to employee stock purchase plan	773		773
Issuance of common stock pursuant to employee stock purchase plan, shares		15,000
Issuance of restricted common stock pursuant to stock-based compensation plans		$ 1	(1)
Issuance of restricted common stock pursuant to stock-based compensation plans, shares		42,000
Cancellation of restricted common stock issued pursuant to stock-based compensation plans		$ (1)	1
Cancellation of restricted common stock issued pursuant to stock-based compensation plans, shares		(60,000)
Stock-based compensation expense	6,536		6,536
Dividends	(8,473)						(8,473)
Write-off of noncontrolling interest	(3,635)								(3,635)
Balance, ending of period at Jun. 30, 2022	$ 377,022	$ 709	$ 479,271		$ (967,659)	$ (55,532)	$ 920,233		$ 0
Balance, ending of period, shares at Jun. 30, 2022	32,195,000	32,195,000