CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net loss	$ (41,420)	$ (52,709)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	5,696	4,787
Share-based compensation	694	4,834
Other	(993)	654
Changes in assets and liabilities:
Accounts receivable	61,329	39,309
Prepaid expenses and other assets	510	7,102
Operating lease right-of-use assets	6,427	4,551
Accounts payable	7,481	4,484
Accrued expenses and other liabilities	(2,024)	2,696
Operating lease liabilities	(4,578)	(2,174)
Net cash provided by operating activities	33,122	13,534
Investing activities
Purchases of property and equipment	(3,706)	(8,240)
Purchases of marketable securities	(113,952)	(83,569)
Sales of marketable securities	28,953	36,408
Maturities of marketable securities	84,883	142,428
Net cash provided by (used in) investing activities	(3,822)	87,027
Financing activities
Proceeds from exercise of stock options, net	110	435
Other financing activities	(3,279)	0
Net cash provided by (used in) financing activities	(3,169)	435
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	8	48
Net increase in cash, cash equivalents, and restricted cash	26,139	101,044
Cash, cash equivalents, and restricted cash, beginning of period	135,290	83,969
Cash, cash equivalents, and restricted cash, end of period	$ 161,429	$ 185,013