Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities:
Net (loss) income	$ 4,962	$ 3,038	$ (2,955)
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Amortization of debt discount	305	801	1,339
Amortization of leasehold interest	(99)	(99)
Depreciation and amortization	10,452	8,666	4,551
Restructuring charge	654		1,549
(Decrease) increase in deferred rent liability	(47)	19	(58)
Amortization of marketing agreement intangible assets	305	174	92
Allowance for doubtful accounts	106	96	23
Deferred income taxes	400	183	305
Stock based compensation	13,259	9,165	3,980
Foreign exchange loss (gain)	(138)	46
Increase in fair value of warrants for redeemable convertible preferred stock			1,996
Decrease in fair value of contingent consideration	(1,041)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable	(5,089)	(5,883)	(4,437)
Prepaid expenses and other current assets	(407)	170	47
Other assets	191	(19)	(381)
Accounts payable	32	1,310	3,054
Accrued expenses	(2,409)	885	(184)
Deferred revenue	(23)	(1,864)	1,226
Net cash provided by operating activities	21,413	16,688	10,147
Investing activities:
Purchases of computers, furniture and equipment	(2,643)	(1,820)	(853)
Cash paid in connection with acquisitions, net of cash received	(20,845)	(38,410)	(22,194)
Net cash used in investing activities	(23,488)	(40,230)	(23,047)
Financing activities:
Repayment of debt	(1,006)	(9,676)	(38,018)
Borrowings of debt		778	20,000
Proceeds from public offerings, net of issuance costs		37,729	66,989
Repurchase of common stock	(8,590)	(2,700)
Proceeds from repayment of notes receivable		93
Deferred financing costs			(170)
Proceeds from exercise of stock options and stock warrants	4,861	4,174	1,593
Net cash provided by (used in) financing activities	(4,735)	30,398	50,394
Effect of exchange rate on cash	(219)	(52)
Net increase (decrease) in cash and cash equivalents	(7,029)	6,804	37,494
Cash and cash equivalents, beginning of period	50,211	43,407	5,913
Cash and cash equivalents, end of period	$ 43,182	$ 50,211	$ 43,407