License and Collaboration Agreements (Tables)

12 Months Ended

Dec. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

License and royalty revenue consisted of the following (in thousands):

	Years Ended December 31,
	2021		2020		2019
AbbVie collaboration and license agreement	$	370,000	$	—	$	—
Royalties on net sales of Zolgensma		94,978		61,631		20,829
Achievement of sales-based milestone for Zolgensma		—		80,000		—
Other license and royalty revenue		5,369		12,936		14,404
Total license and royalty revenue	$	470,347	$	154,567	$	35,233

Summary of Changes in Balances of Receivables, Contract Assets and Deferred Revenue

The following table presents changes in the balances of the Company’s net accounts receivable, contract assets and deferred revenue, as well as other information regarding revenue recognized, during the periods presented (in thousands):

	Years Ended December 31,
	2021			2020			2019
Accounts receivable, net, current and non-current:
Balance, beginning of period	$	46,266		$	42,303		$	31,599
Additions		472,347			158,682			39,203
Deductions		(483,912	)		(154,719	)		(28,499	)
Balance, end of period	$	34,701		$	46,266		$	42,303

Contract assets:
Balance, beginning of period	$	350		$	—		$	750
Additions		1,074			350			1,000
Deductions		(350	)		—			(1,750	)
Balance, end of period	$	1,074		$	350		$	—

Deferred revenue, current and non-current:
Balance, beginning of period	$	4,232		$	3,333		$	3,933
Additions		—			1,124			—
Deductions		(899	)		(225	)		(600	)
Balance, end of period	$	3,333		$	4,232		$	3,333

Revenue recognized during the period from:
Amounts included in deferred revenue at beginning of period	$	390		$	—		$	600
Performance obligations satisfied in previous periods	$	98,575		$	146,772		$	26,689

Summary of Accounts Receivables, net

Accounts receivable, net consisted of the following (in thousands):

	As of December 31,
	2021			2020
Current accounts receivable:
Billed to customers	$	365		$	30,573
Unbilled		32,074			20,104
Allowance for credit losses		—			(7,678	)
Current accounts receivable, net		32,439			42,999
Non-current accounts receivable:
Unbilled		6,020			3,267
Allowance for credit losses		(3,758	)		—
Non-current accounts receivable, net		2,262			3,267
Total accounts receivable, net	$	34,701		$	46,266

Summary of Changes in Allowance For Credit Losses

The following table presents the changes in the allowance for credit losses related to accounts receivable and contract assets for the years ended December 31, 2021 and 2020 (in thousands):

	Allowance for Credit Losses
	Accounts Receivable			Contract Assets
Balance at December 31, 2019	$	—		$	—
Provision for credit losses (recoveries)		7,678			—
Write-offs		—			—
Balance at December 31, 2020		7,678			—
Provision for credit losses (recoveries)		(2,569	)		—
Changes in present value discount of receivables		(1,243	)		—
Write-offs		(108	)		—
Balance at December 31, 2021	$	3,758		$	—

Schedule of AbbVie Collaboration Agreement

The Company recognized the following amounts under the AbbVie Collaboration Agreement (in thousands):

	Year Ended
	December 31, 2021
License and royalty revenue	$	370,000
Reduction of research and development expense for costs reimbursable by AbbVie	$	5,866