CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings (Accumulated Deficit) [Member]
Balance at Dec. 31, 2017	$ 333,154	$ 32	$ 386,196	$ (1,205)	$ (51,869)
Balance, Shares at Dec. 31, 2017		31,604
Issuance of shares through share-based compensation plans, net	122		122
Issuance of shares through share-based compensation plans, net, Shares		169
Net income	15,130				15,130
Share-based compensation	1,507		1,507
Share-based compensation plan withholdings	(839)		(839)
Share-based compensation plan withholdings, Shares		(31)
Currency translation	632			632
Unrealized gain on investments	23			23
Balance at Mar. 31, 2018	349,729	$ 32	386,986	(550)	(36,739)
Balance, shares at Mar. 31, 2018		31,742
Balance at Dec. 31, 2017	333,154	$ 32	386,196	(1,205)	(51,869)
Balance, Shares at Dec. 31, 2017		31,604
Net income	29,827
Unrealized gain on investments	130
Balance at Jun. 30, 2018	365,990	$ 32	389,298	(1,298)	(22,042)
Balance, shares at Jun. 30, 2018		31,901
Balance at Mar. 31, 2018	349,729	$ 32	386,986	(550)	(36,739)
Balance, Shares at Mar. 31, 2018		31,742
Issuance of shares through share-based compensation plans, net	368		368
Issuance of shares through share-based compensation plans, net, Shares		164
Net income	14,697				14,697
Share-based compensation	2,081		2,081
Share-based compensation plan withholdings	(137)		(137)
Share-based compensation plan withholdings, Shares		(5)
Currency translation	(855)			(855)
Unrealized gain on investments	107			107
Balance at Jun. 30, 2018	365,990	$ 32	389,298	(1,298)	(22,042)
Balance, shares at Jun. 30, 2018		31,901
Balance at Dec. 31, 2018	361,888	$ 31	369,893	(1,263)	(6,773)
Balance, Shares at Dec. 31, 2018		30,906
Issuance of shares through share-based compensation plans, net, Shares		103
Repurchase of common stock	(744)		(744)
Repurchase of common stock, Shares		(37)
Net income	7,576				7,576
Share-based compensation	2,163		2,163
Share-based compensation plan withholdings	(598)		(598)
Share-based compensation plan withholdings, Shares		(27)
Currency translation	(518)			(518)
Unrealized gain on investments	95			95
Balance at Mar. 31, 2019	369,862	$ 31	370,714	(1,686)	803
Balance, shares at Mar. 31, 2019		30,945
Balance at Dec. 31, 2018	361,888	$ 31	369,893	(1,263)	(6,773)
Balance, Shares at Dec. 31, 2018		30,906
Net income	13,102
Unrealized gain on investments	209
Balance at Jun. 30, 2019	377,500	$ 31	372,396	(1,256)	6,329
Balance, shares at Jun. 30, 2019		31,116
Balance at Mar. 31, 2019	369,862	$ 31	370,714	(1,686)	803
Balance, Shares at Mar. 31, 2019		30,945
Issuance of shares through share-based compensation plans, net	160		160
Issuance of shares through share-based compensation plans, net, Shares		177
Net income	5,526				5,526
Share-based compensation	1,673		1,673
Share-based compensation plan withholdings	(151)		(151)
Share-based compensation plan withholdings, Shares		(6)
Currency translation	316			316
Unrealized gain on investments	114			114
Balance at Jun. 30, 2019	$ 377,500	$ 31	$ 372,396	$ (1,256)	$ 6,329
Balance, shares at Jun. 30, 2019		31,116