Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Statement of Cash Flows [Abstract]
Net loss	$ (24,374)	$ (33,758)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	17,481	17,711
Deferred income taxes	399	437
Bad debt expense and other reserves	1,062	817
Stock-based compensation	22,661	18,033
Common stock warrant expense	0	13
Non-cash interest expense on lease financing obligation	312	314
Write-off and loss on disposal of fixed assets	148	392
Changes in operating assets and liabilities:
Accounts receivable	(3,782)	(2,928)
Prepaid expenses	(1,070)	(1,181)
Other current assets	(167)	(638)
Other assets	(36)	(311)
Accounts payable	7,400	(5,134)
Accrued employee expenses	(2,835)	756
Accrued expenses and other liabilities	(1,081)	1,479
Other liabilities	795	1,396
Net cash provided by (used in) operating activities	16,913	(2,602)
Cash flows from investing activities
Purchase of property and equipment	(15,194)	(12,872)
Net cash used in investing activities	(15,194)	(12,872)
Cash flows from financing activities
Proceeds from public offering, net of underwriting discounts and offering costs	17,398	0
Repurchase of common stock option awards	0	(100)
Proceeds from exercise of common stock options	71,868	5,406
Taxes paid related to net share settlement of equity awards	(2,304)	(751)
Proceeds from financing obligation drawdown	0	1,521
Net cash provided by financing activities	86,962	6,076
Net increase (decrease) in cash and cash equivalents	88,681	(9,398)
Cash and cash equivalents at beginning of period	107,721	112,371
Cash and cash equivalents at end of period	196,402	102,973
Supplemental disclosures of non-cash activities
Stock-based compensation capitalized for software development	993	760
Capitalized assets included in accounts payable, accrued employee expenses and other accrued expenses	909	143
Proceeds receivable from exercise of stock options included in other current assets	530	0
Taxes payable related to net share settlement of equity awards included in accrued employee expenses	$ 220	$ 0