CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities
Net loss	$ (4,318)	$ (2,617)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization expense	6,785	5,217
Share-based compensation expense	15,038	11,642
Amortization of debt discount and issuance costs	4,005	0
Operating lease expense, net of accretion	1,049	0
Other non-cash items	(44)	(41)
Change in assets and liabilities:
Accounts receivable	4,024	2,783
Prepaid expenses and other current assets	(11,522)	(7,894)
Other assets	(1,166)	(506)
Accounts payable	(1,836)	(3,068)
Deferred revenue	8,858	5,185
Accrued liabilities	216	(4,286)
Other liabilities	(3,148)	138
Net cash provided by operating activities	17,941	6,553
Cash flows from investing activities
Purchases of marketable securities	(21,572)	(12,511)
Maturities of marketable securities	48,805	21,630
Purchases of property and equipment	(14,060)	(4,883)
Net cash provided by investing activities	13,173	4,236
Cash flows from financing activities
Common stock issued under stock plans, net	6,982	5,222
Payment of taxes related to the net share settlement of equity awards	(76,044)	(35,640)
Proceeds from issuance of convertible senior notes, net of issuance costs	682,594	0
Purchase of convertible senior notes capped call	(85,050)	0
Repurchase of common stock	(20,000)	0
Net cash provided by (used in) financing activities	508,482	(30,418)
Net increase (decrease) in cash, cash equivalents and restricted cash	539,596	(19,629)
Cash, cash equivalents and restricted cash, beginning of period	375,945	126,963
Cash, cash equivalents and restricted cash, end of period	915,541	107,334
Supplemental cash flow data:
Interest	0	19
Income taxes	626	503
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	1,126	0
Non-cash investing activities:
Accrued purchases of long-lived assets	$ 5,127	$ 3,204