Deferred Revenue (Tables)

6 Months Ended

Jun. 30, 2019

Revenue From Contract With Customer [Abstract]

Deferred Revenue by Revenue Classification

Deferred revenue by revenue classification was as follows (in thousands):

	June 30, 2019		December 31, 2018
	(unaudited)
Current deferred revenue
Sequencing	$	14,616	$	11,238
Development		46,578		1,457
Total current deferred revenue		61,194		12,695
Non-current deferred revenue
Sequencing		493		516
Development		240,426		188
Total non-current deferred revenue		240,919		704
Total current and non-current deferred revenue	$	302,113	$	13,399

Changes in Deferred Revenue

Changes in deferred revenue during the six months ended June 30, 2019 were as follows (in thousands):

Deferred revenue balance at December 31, 2018	$	13,399
Additions to deferred revenue during the period (unaudited)		308,055
Revenue recognized during the period (unaudited)		(19,341	)
Deferred revenue balance at June 30, 2019 (unaudited)	$	302,113