Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net income	$ 46,514	$ 41,635	$ 35,277
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,126	11,138	7,569
Stock-based compensation expense	6,082	4,809	3,461
Deferred taxes	2,837	(1,875)	467
Excess tax benefit from stock-based compensation	$ (5,539)	$ (4,470)	(9,873)
Loss on disposal of property and equipment			$ 110
Gain on acquisition	$ (344)
Amortization of held-to-maturity securities	1,234	$ 1,517	$ 1,468
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	(11,371)	(5,304)	(2,470)
Inventories	(2,097)	(896)	(579)
Prepaid expenses and other	(2,047)	107	1,630
Income taxes	(2,310)	9,373	8,845
Accounts payable	5,781	1,435	1,651
Accrued liabilities and other	5,691	(259)	885
Net cash provided by operating activities	58,557	57,210	48,441
Investing activities
Purchases of property and equipment	(44,362)	(43,507)	$ (18,753)
Cash used for acquisitions, net of cash acquired	(5,032)	(33,864)
Purchases of marketable securities	(66,393)	(60,186)	$ (106,298)
Proceeds from maturities of marketable securities	52,193	74,058	66,570
Net cash used in investing activities	(63,594)	(63,499)	(58,481)
Financing activities
Payments on debt	(152)	(1,054)	$ (258)
Acquisition-related contingent consideration	(1,400)	(1,200)
Proceeds from exercises of stock options and other	6,251	4,820	$ 6,496
Excess tax benefit from stock-based compensation	5,539	4,470	9,873
Net cash provided by financing activities	10,238	7,036	16,111
Effect of exchange rate changes on cash and cash equivalents	(877)	(457)	209
Net increase in cash and cash equivalents	4,324	290	6,280
Cash and cash equivalents, beginning of period	43,329	43,039	36,759
Cash and cash equivalents, end of period	47,653	43,329	43,039
Supplemental cash flow disclosure
Cash paid for interest	5	19	35
Cash paid for taxes	$ 20,330	$ 11,549	$ 6,593