Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Cash flows from operating activities:
Net loss	$ (6,048)	$ (7,040)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of deferred implementation, solution and other costs	2,218	1,719
Depreciation and amortization	3,878	3,525
Amortization of debt issuance costs	123	24
Amortization of premiums on investments	56	69
Amortization of debt discount	1,099	0
Stock-based compensation expenses	6,095	4,197
Deferred income taxes	36	117
Allowance for sales credits	22	(10)
Loss on disposal of long-lived assets	0	4
Changes in operating assets and liabilities:
Accounts receivable, net	(3,717)	3,802
Prepaid expenses and other current assets	(1,727)	(2,805)
Deferred solution and other costs	(3,493)	(2,066)
Deferred implementation costs	(1,181)	(1,314)
Contract assets	(816)	0
Other long-term assets	(220)	(28)
Accounts payable	(1,054)	1,293
Accrued liabilities	(4,307)	(8,756)
Deferred revenues	2,250	(3,114)
Deferred rent and other long-term liabilities	(317)	(285)
Net cash used in operating activities	(7,103)	(10,668)
Cash flows from investing activities:
Purchases of investments	0	(2,939)
Maturities of investments	2,901	5,709
Purchases of property and equipment	(5,396)	(5,361)
Business combinations and asset acquisitions, net of cash acquired	(150)	(1,316)
Capitalized software development costs	0	(532)
Net cash used in investing activities	(2,645)	(4,439)
Cash flows from financing activities:
Proceeds from issuance of convertible notes, net of issuance costs	223,675	0
Purchase of convertible notes bond hedge	(41,699)	0
Proceeds from issuance of warrants	22,379	0
Proceeds from exercise of stock options to purchase common stock	2,843	2,990
Net cash provided by financing activities	207,198	2,990
Net increase (decrease) in cash, cash equivalents, and restricted cash	197,450	(12,117)
Cash, cash equivalents, and restricted cash, beginning of period	60,276	56,188	$ 56,188
Cash, cash equivalents, and restricted cash end of period	257,726	44,071	60,276
Supplemental disclosures of cash flow information:
Cash paid for interest	0	43
Supplemental disclosure of non-cash investing and financing activities:
Shares acquired to settle the exercise of stock options	(62)	(39)
Reconciliation of cash, cash equivalents, and restricted cash as shown in the statement of cash flows:
Cash and cash equivalents				$ 255,411	$ 57,961	$ 42,756
Restricted cash				2,315	2,315	1,315
Total cash, cash equivalents, and restricted cash	$ 60,276	$ 56,188	$ 56,188	$ 257,726	$ 60,276	$ 44,071