Summary of Basis of Presentation and Recent Accounting Standards (Tables)

9 Months Ended

Sep. 30, 2020

Accounting Policies [Abstract]

Effect of Adoption of 842 on Condensed Financial Statements

The following tables summarize the effects of adopting ASC 842 on our condensed consolidated financial statements for the three and nine months ended September 30, 2019 (in thousands, except per share data):

	Three Months Ended September 30, 2019						Nine Months Ended September 30, 2019
			ASC 842						ASC 842
	Previously reported		Adjustments		As adjusted		Previously reported		Adjustments		As adjusted
Operating expenses:
Research and development	$	119,715	$	(78)	$	119,637	$	378,786	$	(431)	$	378,355
General and administrative	28,188		(15)		28,173		83,994		(81)		83,913
Total operating expenses	147,903		(93)		147,810		462,780		(512)		462,268
Loss from operations	(130,857)		93		(130,764)		(416,626)		512		(416,114)
Other expense, net	(1,767)		(114)		(1,881)		(5,351)		(338)		(5,689)
Loss before benefit from income taxes	(123,372)		(21)		(123,393)		(391,431)		174		(391,257)
Net loss	(123,194)		(21)		(123,215)		(390,905)		174		(390,731)
Net loss per share attributable to common stockholders, basic and diluted	(0.37)		—		(0.37)		(1.19)		—		(1.19)

	Nine Months Ended September 30, 2019
	Previously reported		ASC 842 Adjustment during the period		As adjusted
Operating activities
Net loss	$	(390,905)	$	174	$	(390,731)
Depreciation and amortization	22,082		(36)		22,046
Prepaid expenses and other assets	(1,407)		3,220		1,813
Right-of-use assets, operating leases	—		(7,970)		(7,970)
Deferred lease obligation	3,844		(3,844)		—
Operating lease liabilities	—		13,475		13,475
Other liabilities	1,617		(1,770)		(153)
Net cash used in operating activities	(363,195)		3,249		(359,946)
Financing activities
Reimbursement of assets under lease financing obligation	3,678		(3,678)		—
Charges to financing lease obligation	—		741		741
Payments on financing lease obligation	312		(312)		—
Net cash provided by financing activities	23,531		(3,249)		20,282

Components of Accumulated Other Comprehensive Income

The components of accumulated other comprehensive (loss) income for the three and nine months ended September 30, 2020 are as follows (in thousands): 

	Unrealized (Loss) Gain on Available-for-Sale Debt Securities
Accumulated other comprehensive income, balance at December 31, 2019	$	1,804
Other comprehensive loss	(7,931)
Accumulated other comprehensive loss, balance at March 31, 2020	(6,127)
Other comprehensive income	14,383
Accumulated other comprehensive income, balance at June 30, 2020	8,256
Other comprehensive loss	(3,472)
Accumulated other comprehensive income, balance at September 30, 2020	$	4,784

Reconciliation of Cash and Cash Equivalents

The following table provides a reconciliation of cash, cash equivalents and restricted cash in the condensed consolidated balance sheets that sum to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands):

	September 30,
	2020		2019
Cash and cash equivalents	$	1,505,581	$	173,711
Restricted cash	1,032		1,032
Restricted cash, non-current	11,053		10,791
Total cash, cash equivalents and restricted cash shown in the condensed consolidated statements of cash flows	$	1,517,666	$	185,534

Reconciliation of Restricted Cash

The following table provides a reconciliation of cash, cash equivalents and restricted cash in the condensed consolidated balance sheets that sum to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands):

	September 30,
	2020		2019
Cash and cash equivalents	$	1,505,581	$	173,711
Restricted cash	1,032		1,032
Restricted cash, non-current	11,053		10,791
Total cash, cash equivalents and restricted cash shown in the condensed consolidated statements of cash flows	$	1,517,666	$	185,534