CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income	$ 3,642	$ 2,365
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	3,597	2,092
Depreciation	8,874	6,567
Amortization of intangibles	3,611	1,827
Amortization of premiums on short-term investments	591	871
Realized losses on short-term investments		4
Tax payments for equity award issuances		88
Deferred income taxes	(113)	(1,252)
Excess tax benefits from stock-based compensation		(911)
Gain on disposal of equipment		(534)
Changes in assets and liabilities:
Accounts receivable	(16,049)	8,128
Prepaid expenses and other current assets	(886)	(5,054)
Income taxes receivable	2,381	2,037
Other assets	(890)	78
Accounts payable	69	(2,194)
Accrued compensation	(6,467)	(3,877)
Other liabilities	(816)	2,676
Deferred rent	(214)	(149)
Deferred revenue	5,001	1,537
Net cash provided by operating activities	2,331	14,299
Cash flows from investing activities:
Sales and maturities of short-term investments	59,615	84,671
Purchases of short-term investments		(80,065)
Purchases of property and equipment	(2,965)	(4,053)
Investment in capitalized software	(5,605)	(2,790)
Net cash provided by (used in) investing activities	51,045	(2,237)
Cash flows from financing activities:
Repurchase of common stock	(25,383)
Repayment of credit facility borrowings	(7,500)	(3,750)
Proceeds from exercise of stock options	25	3,841
Capital lease obligations paid	(116)	(31)
Tax payments for equity award issuances	(197)	(182)
Excess tax benefits from stock-based compensation		911
Net cash (used in) provided by financing activities	(33,171)	789
Increase in cash and cash equivalents	20,205	12,851
Cash and cash equivalents, beginning of period	127,683	114,034
Cash and cash equivalents, end of period	147,888	126,885
Supplementary cash flow disclosure:
Cash paid during the period for: Income taxes, net of refunds	189	861
Cash paid during the period for: Interest	1,364	1,195
Non-cash investing activities:
Accounts payable for purchases of and investment in property, equipment and capitalized software	2,737	933
Accrued compensation for investment in capitalized software	$ 2,992	$ 53