Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Operating activities:
Net income	$ 4,276,000	$ 8,116,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,624,000	1,237,000
Stock-based compensation expense	4,957,000	4,554,000
Amortization of acquired intangible assets	425,000	0
Deferred taxes	192,000	997,000
Loss on disposal of property and equipment	107,000	3,000
Purchases of treasury stock in connection with tax withholdings on restricted stock grants	(1,075,000)	(1,052,000)
Reversal of allowance for doubtful accounts	(99,000)	(82,000)
Unrealized loss (gain) on foreign currency forward contract	(34,000)	3,000
Tax benefit related to stock-based compensation expense	748,000	2,094,000
Excess tax benefit from stock-based compensation	(708,000)	(1,980,000)
Changes in operating assets and liabilities:
Accounts receivable	(1,249,000)	6,861,000
Prepaid expenses and other assets	(8,908,000)	(4,428,000)
Accounts payable	610,000	(39,000)
Accrued compensation and related benefits	346,000	(1,521,000)
Accrued and other liabilities	(223,000)	256,000
Deferred revenues	947,000	1,774,000
Billings in excess of recognized revenues	(955,000)
Net cash provided by operating activities	981,000	16,793,000
Investing activities:
Purchases of property and equipment	(5,051,000)	(2,388,000)
Net cash used in investing activities	(5,051,000)	(2,388,000)
Financing activities:
Proceeds from exercise of stock options	452,000	4,764,000
Proceeds from employee stock purchase plan	778,000	680,000
Excess tax benefit from stock-based compensation	708,000	1,980,000
Purchases of treasury stock	(1,843,000)	(5,571,000)
Net cash provided by financing activities	95,000	1,853,000
Effect of exchange rate changes on cash and cash equivalents	39,000	(23,000)
Net change in cash and cash equivalents	(3,936,000)	16,235,000
Cash and cash equivalents, beginning of period	126,158,000	115,464,000
Cash and cash equivalents, end of period	122,222,000	131,699,000
Supplemental disclosure of cash flow information:
Taxes	1,336,000	3,920,000
Property and equipment received and accrued in accounts payable and accrued and other liabilities	$ 1,656,000	$ 582,000