Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes
Research and development tax credit	(13.70%)	(12.60%)	0.70%
Previously taxed foreign income, repatriated	$ 1,300,000	$ 1,000,000	$ 2,500,000
Undistributed foreign earnings	201,700,000
U.S. statutory rate	35.00%	35.00%	35.00%
U.S. deferred tax asset	200,000
U.S. deferred assets, net operating loss carryforwards	400,000
Unrecognized tax benefits	2,479,000
Unrecognized tax benefits would impact the effective tax rate	1,700,000
Interest expense related to unrecognized tax benefits		(1,000,000)	400,000
Interest accrued	292,000	300,000
Tax credit carryforward, expiration date	2016
Tax credit carryforward tax assets	10,500,000	8,700,000
Valuation allowances	2,311,000	77,000
Federal
Income Taxes
Cash and cash equivalents and short-term investments	139,100,000	160,500,000
Operating loss carryforwards	14,700,000	0
Foreign
Income Taxes
Cash and cash equivalents and short-term investments	206,400,000	196,900,000
Operating loss carryforwards	$ 3,400,000	$ 4,400,000