Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating activities
Net income	$ 8,287	$ 4,782
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,734	1,328
Stock-based compensation expense	865	850
Deferred taxes	148
Excess tax benefit from stock-based compensation	(4,067)
Amortization of held-to-maturity securities	304
Changes in operating assets and liabilities:
Accounts receivable	(1,929)	(3,180)
Inventories	(183)	(100)
Prepaid expenses and other	393	29
Income taxes	2,719	1,991
Accounts payable	1,115	1,344
Accrued liabilities and other	1,759	367
Net cash provided by operating activities	11,145	7,411
Investing activities
Purchases of property and equipment	(2,548)	(8,264)
Purchases of marketable securities	(41,088)
Proceeds from maturities of marketable securities	18,313	250
Net cash used in investing activities	(25,323)	(8,014)
Financing activities
Proceeds from initial public offering, net of offering costs		71,675
Payments on debt	(92)	(94)
Proceeds from exercises of warrants and stock options	1,619	30
Excess tax benefit from stock-based compensation	4,067
Net cash provided by financing activities	5,594	71,611
Effect of exchange rate changes on cash and cash equivalents	(246)	536
Net increase (decrease) in cash and cash equivalents	(8,830)	71,544
Cash and cash equivalents, beginning of period	36,759	8,135
Cash and cash equivalents, end of period	$ 27,929	$ 79,679