Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Operating activities
Net income	$ 21,058	$ 16,898
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,683	3,582
Stock-based compensation expense	2,248	1,736
Deferred taxes	107	307
Excess tax benefit from stock-based compensation	(1,623)	(5,929)
Loss on disposal of property and equipment		59
Amortization of held-to-maturity securities	854	633
Changes in operating assets and liabilities:
Accounts receivable	(5,742)	(2,032)
Inventories	(306)	(360)
Prepaid expenses and other	(372)	1,715
Income taxes	2,431	3,066
Accounts payable	5,143	1,083
Accrued liabilities and other	(2,464)	(1,310)
Net cash provided by operating activities	26,017	19,448
Investing activities
Purchases of property and equipment	(31,625)	(6,069)
Acquisitions, net of cash acquired	(33,864)
Purchases of marketable securities	(38,463)	(57,310)
Proceeds from maturities of marketable securities	55,441	34,280
Net cash used in investing activities	(48,511)	(29,099)
Financing activities
Payments on debt	(954)	(166)
Acquisition-related contingent consideration	(400)
Proceeds from exercises of stock options and other	1,806	2,870
Excess tax benefit from stock-based compensation	1,623	5,929
Net cash provided by financing activities	2,075	8,633
Effect of exchange rate changes on cash and cash equivalents	234	(295)
Net decrease in cash and cash equivalents	(20,185)	(1,313)
Cash and cash equivalents, beginning of period	43,039	36,759
Cash and cash equivalents, end of period	$ 22,854	$ 35,446