Stock-Based Compensation Expense - Effect of Recording Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 33,462	$ 21,101	$ 11,517
Tax effect on stock-based compensation expense	(5,296)	(6,314)	(3,107)
Net effect on net income	28,166	14,787	8,410
Cost of revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0	0	0
Research, development and other related costs
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	13,277	7,104	4,005
Selling, general and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 20,185	$ 13,997	$ 7,512