Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Provision For Income Taxes [Line Items]
Tax rate	35.00%	35.00%
Income before income taxes	$ 46,081	$ 38,241
Income tax at federal statutory tax rate	16,128	13,384
Tax benefit of double-deductible R&D expense	(2,871)	(2,793)
Effect of differences in foreign tax rate	(7,756)	(6,175)
Provision on valuation allowance for deferred income tax	9,236	8,918	8,988
Other differences	799	1,138
Total income tax expense	6,785	5,483
U S [Member]
Schedule Provision For Income Taxes [Line Items]
Provision on valuation allowance for deferred income tax	188	(178)
PRC [Member]
Schedule Provision For Income Taxes [Line Items]
Provision on valuation allowance for deferred income tax	$ 297	$ 107