Revenues

6 Months Ended

Jun. 30, 2020

Revenue from Contract with Customer [Abstract]

Revenues

Revenues

The following table presents a summary of total revenues (in thousands): 

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Xyrem	$	446,808	$	413,212	$	854,683	$	781,529
Defitelio/defibrotide	42,714		46,055		90,146		87,555
Erwinaze/Erwinase	32,683		27,622		70,415		88,521
Vyxeos	26,568		31,362		59,288		60,305
Sunosi	8,578		—		10,502		—
Other	852		5,172		3,374		8,844
Product sales, net	558,203		523,423		1,088,408		1,026,754
Royalties and contract revenues	4,233		10,710		8,754		15,565
Total revenues	$	562,436	$	534,133	$	1,097,162	$	1,042,319

The following table presents a summary of total revenues attributed to geographic sources (in thousands): 

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
United States	$	516,097	$	480,932	$	994,580	$	943,794
Europe	37,895		36,518		79,451		71,919
All other	8,444		16,683		23,131		26,606
Total revenues	$	562,436	$	534,133	$	1,097,162	$	1,042,319

The following table presents a summary of the percentage of total revenues from customers that represented more than 10% of our total revenues: 

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
ESSDS	79	%	77	%	78	%	75	%
McKesson	10	%	12	%	11	%	15	%

Financing and payment

Our payment terms vary by the type and location of our customer but payment is generally required in a term ranging from 30 to 45 days.

Contract Liabilities - Deferred Revenue

The deferred revenue balance as of June 30, 2020 primarily related to deferred upfront fees received from Nippon Shinyaku Co., Ltd., or Nippon Shinyaku, in connection with two license, development and commercialization agreements granting Nippon Shinyaku exclusive rights to develop and commercialize each of Defitelio and Vyxeos in Japan. We recognized contract revenues of $1.2 million and $2.4 million during the three and six months ended June 30, 2020, respectively, relating to these upfront payments. The deferred revenue balances are being recognized over an average of four

years representing the period over which we expect to perform our research and developments obligations under each agreement.

The following table presents a reconciliation of our beginning and ending balances in contract liabilities from contracts with customers for the six months ended June 30, 2020 (in thousands): 

	Contract Liabilities
Balance as of December 31, 2019	$	9,581
Amount recognized within royalties and contract revenues	(2,360		)
Balance as of June 30, 2020	$	7,221