Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating activities:
Net income	$ 77,105	$ 61,646
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	5,656	4,652
Equity-based compensation	11,087	6,967
Gain on disposal of equipment	(38)	(23)
Tax benefit of stock awards exercised/vested	8,435	7,395
Excess tax benefits from equity-based compensation	(8,413)	(7,359)
Deferred income taxes	712	122
Unrealized foreign currency loss (gain)	86	(36)
Changes in operating assets and liabilities:
Accounts receivable, net	(6,609)	(17,147)
Other assets	(1,592)	(6,408)
Accounts payable, accrued and other liabilities	(8,444)	1,564
Income taxes	(602)	(2,442)
Deferred revenue	6,651	4,786
Net cash provided by operating activities	84,034	53,717
Investing activities:
Purchase of property and equipment	(9,619)	(6,676)
Net purchases of investments	(1,825)	(1,849)
Payment in connection with acquisition		(2,773)
Net cash used in investing activities	(11,444)	(11,298)
Financing activities:
Purchase of common stock	(86,839)	(73,706)
Proceeds from issuance of common stock from options exercised	568	1,014
Excess tax benefits from equity-based compensation	8,413	7,359
Net cash used in financing activities	(77,858)	(65,333)
Foreign currency impact on cash	(1,411)	(345)
Net change in cash and cash equivalents	(6,679)	(23,259)
Cash and cash equivalents at beginning of period	115,708	124,375
Cash and cash equivalents at end of period	$ 109,029	$ 101,116