Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (88,205,772)	$ (73,740,339)	$ (29,102,837)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,850,376	1,708,498	1,048,431
Amortization of intangible assets	1,618,665	1,377,466	870,199
Change in value of common stock warrants	(806,819)	(127,554)	(177,561)
Stock-based compensation	13,070,962	10,479,135	6,186,848
Amortization of premiums on investments	319,845	266,290	348,566
Deferred taxes	(150,027)	(849)	14,166
Deferred rent	3,608,881	(16,728)	383,584
Loss on short-term investments	215,423	139,249	432,174
Gain on investment in affiliated entity	6,982,664	(1,110,787)	(2,600,467)
Gain on sale of intangible assets	(1,000,000)	(1,000,000)	(1,000,000)
Income tax benefit from other unrealized gains on securities	0	0	(2,097,766)
Changes in operating assets and liabilities:
Accounts receivable	9,818,306	(8,521,899)	(4,497,225)
Accounts receivable from affiliated entity	261,736	(714,908)	(31,627)
Prepaid expenses and other current assets	(851,847)	(831,802)	(119,284)
Prepaid expenses and other current assets from affiliated entity	(333,583)	(901,772)	771,723
Other assets	(526,207)	(1,442,314)	(196,265)
Accounts payable and accrued expenses	2,829,807	6,367,965	6,456,581
Accrued clinical trial expenses	2,243,503	3,767,906	593,051
Accounts payable and accrued expenses due to affiliated entity	(145,636)	907,532	136,640
Deferred revenue	(13,689,322)	1,527,686	10,191,840
Deferred revenue from affiliated entity	(319,876)	(687,827)	(49,672)
Net cash used in operating activities	(63,208,921)	(62,555,052)	(12,438,901)
Cash flows from investing activities:
Purchases of investments	(95,700,144)	(57,317,671)	(63,526,830)
Maturities of investments	77,162,902	76,528,030	10,484,267
Purchases of capital assets	(10,293,902)	(2,738,470)	(2,781,544)
Proceeds from sale of intangible assets	1,000,000	1,000,000	1,000,000
Purchase of intangible and other assets	0	(1,200,000)	0
Net cash provided by (used in) investing activities	(27,831,144)	16,271,889	(54,824,107)
Cash flows from financing activities:
Proceeds from issuance of common stock and warrants, net of issuance costs	94,347,922	6,295,761	81,902,363
Proceeds from stock option and warrant exercises, net of tax payments	1,342,250	1,640,740	2,598,915
Expenses from other financing activities	0	(149,559)	(149,559)
Net cash provided by financing activities	95,690,172	7,786,942	84,351,719
Increase (Decrease) in cash and cash equivalents	4,650,107	(38,496,221)	17,088,711
Cash and cash equivalents, beginning of period	19,136,472	57,632,693	40,543,982
Cash and cash equivalents, end of period	23,786,579	19,136,472	57,632,693
Supplemental disclosure of non-cash activities
Common stock issued for purchase of Bioject	0	4,300,000	0
Change in amounts accrued for purchases of property and equipment	851,204	164,923	225,148
Lease incentive recorded as fixed assets and deferred rent	$ 0	$ 523,856	$ 773,000