Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash Flows from Operating Activities
Net loss	$ (41,211)	$ (26,531)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,659	739
Amortization of intangible assets	268	277
Accretion of discounts and amortization of premiums on marketable securities	497	1,045
Stock-based compensation	7,985	7,068
Excess tax benefit from stock-based compensation		(2,185)
Gain from remeasurement of fair value of contingent consideration	1,636	(317)
Loss on disposal of property and equipment	5
Deferred income tax	1,272
Changes in operating assets and liabilities:
Accounts receivable	(2,238)	3,462
Prepaid expenses and other assets	(5,832)	(9,074)
Restricted cash		(468)
Accounts payable	607	(2,814)
Deferred revenue	(7,514)	(7,542)
Accrued clinical trial and manufacturing expenses	(576)	8,356
Accrued expenses and other liabilities	(670)	2,094
Net cash used in operating activities	(44,112)	(25,890)
Cash Flows from Investing Activities
Purchase of marketable securities	(140,626)	(244,250)
Proceeds from maturities of marketable securities	233,678	233,108
Purchase of property and equipment	(1,453)	(10,536)
Net cash provided by (used in) investing activities	91,599	(21,678)
Cash Flows from Financing Activities
Proceeds from employee stock purchase plan	494	514
Excess tax benefit from stock-based compensation		2,185
Proceeds from exercise of stock options and warrants	435	351
Proceeds from issuance of common stock, net of offering costs	60,467
Net cash provided by financing activities	61,396	3,050
Net increase (decrease) in cash and cash equivalents	108,883	(44,518)
Cash and cash equivalents at beginning of period	74,932	150,456
Cash and cash equivalents at end of period	183,815	105,938
Supplemental Disclosure of Cash Flow Information
Cash paid for taxes	850	8,600
Supplemental Disclosure of Non-Cash Investing and Financing Activities
Purchase of property and equipment in accounts payable and accrued liabilities	$ 219	$ 4,135