CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Ordinary Shares	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2014		45,487,764
Common stock, amount outstanding, beginning balance at Dec. 31, 2014		$ 192
Beginning balance, value at Dec. 31, 2014	$ 701,752		$ 615,148	$ (4,020)	$ 90,432
Increase (Decrease) in Stockholders' Equity
Net income	92,894				92,894
Unrealized losses on available-for-sale securities, net of taxes	(204)			(204)
Unrealized gain on derivative contracts, net of taxes	2,555			2,555
Share-based compensation	50,764		50,764
Issuance of shares through employee equity incentive plans (in shares)		1,267,244
Issuances of shares through employee equity incentive plans	6,049	$ 6	6,043
Issuance of shares through employee share purchase plan (in shares)		364,746
Issuance of shares through employee share purchase plan	12,818	$ 2	12,816
Income tax benefit from share options exercised	53		53
Ending balance (in shares) at Dec. 31, 2015		47,119,754
Common stock, amount outstanding, ending balance at Dec. 31, 2015		$ 200
Ending balance, value at Dec. 31, 2015	866,681		684,824	(1,669)	183,326
Increase (Decrease) in Stockholders' Equity
Net income	18,518				18,518
Unrealized losses on available-for-sale securities, net of taxes	342			342
Unrealized gain on derivative contracts, net of taxes	399			399
Share-based compensation	66,309		66,309
Issuance of shares through employee equity incentive plans (in shares)		1,463,884
Issuances of shares through employee equity incentive plans	5,090	$ 7	5,083
Issuance of shares through employee share purchase plan (in shares)		491,968
Issuance of shares through employee share purchase plan	17,465	$ 2	17,463
Income tax benefit from share options exercised	(46)		(46)
Fair value of awards attributable to pre-acquisition services	972		972
Ending balance (in shares) at Dec. 31, 2016		49,075,606
Common stock, amount outstanding, ending balance at Dec. 31, 2016		$ 209
Ending balance, value at Dec. 31, 2016	975,730		774,605	(928)	201,844
Increase (Decrease) in Stockholders' Equity
Effect of adopting ASU 2016-09: Improvements to Employee Share-Based Payment Accounting	0		789		(789)
Effect of adopting ASU 2016-09: Improvements to Employee Share-Based Payment Accounting | Accounting Standards Update 2016-09			800
Net income	(19,425)				(19,425)
Unrealized losses on available-for-sale securities, net of taxes	929			929
Unrealized gain on derivative contracts, net of taxes	1,617			1,617
Share-based compensation	68,864		68,864
Issuance of shares through employee equity incentive plans (in shares)		1,843,168.00
Issuances of shares through employee equity incentive plans	7,642	$ 9	7,633
Issuance of shares through employee share purchase plan (in shares)		568,876.00
Issuance of shares through employee share purchase plan	22,091	$ 3	22,088
Ending balance (in shares) at Dec. 31, 2017		51,487,650.00
Common stock, amount outstanding, ending balance at Dec. 31, 2017		$ 221
Ending balance, value at Dec. 31, 2017	$ 1,057,448		$ 873,979	$ 1,618	181,630
Increase (Decrease) in Stockholders' Equity
Effect of adopting ASU 2016-09: Improvements to Employee Share-Based Payment Accounting | Accounting Standards Update 2016-09					$ 800