Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Cash Flows [Abstract]
Net loss	$ (14,365)	$ (9,055)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	6,415	5,169
Deferred income taxes	72	(73)
Bad debt expense and other reserves	348	335
Stock-based compensation	8,635	9,097
Increase in the fair value of contingent consideration liability	75	0
Amortization of lease right-of-use assets	1,465	0
Non-cash interest expense on lease financing obligation	0	173
Write-off and loss on disposal of fixed assets	0	5
Changes in operating assets and liabilities:
Accounts receivable	9,044	1,502
Prepaid expenses	384	(157)
Other current assets	(3,493)	(347)
Other assets	263	(151)
Accounts payable	(5,578)	(1,128)
Accrued employee expenses	275	(3,114)
Operating lease liabilities	(1,398)	0
Accrued expenses and other liabilities	5,498	917
Other liabilities	(59)	270
Net cash provided by operating activities	7,581	3,443
Cash flows from investing activities
Purchase of property and equipment	(2,905)	(5,332)
Payments to Acquire Equity Method Investments	(23,174)	0
Net cash used in investing activities	(26,079)	(5,332)
Cash flows from financing activities
Proceeds from exercise of common stock options	2,811	681
Taxes paid related to net share settlement of equity awards	(543)	(732)
Net cash provided by (used in) financing activities	2,268	(51)
Net decrease in cash and cash equivalents	(16,230)	(1,940)
Cash and cash equivalents at beginning of period	196,128	197,762
Cash and cash equivalents at end of period	179,898	195,822
Supplemental disclosures of non-cash activities
Stock-based compensation capitalized for software development	473	334
Capitalized assets included in accounts payable, accrued employee expenses and other accrued expenses	176	918
Proceeds receivable from exercise of stock options included in other current assets	0	2
Taxes payable related to net share settlement of equity awards included in accrued employee expenses	$ 0	$ 111