Revenue recognition

12 Months Ended

Dec. 31, 2019

Revenue from Contract with Customer [Abstract]

The Company operates in one business segment. Therefore, results of the Company's operations are reported on a consolidated basis for purposes of segment reporting, consistent with internal management reporting.

For the years ended December 31, 2019, 2018 and 2017 the Company's revenues disaggregated by the major sources was as follows:



(in millions)	Year Ended December 31,
	2019						2018						2017
	U.S Government		Non-U.S. Government		Total		U.S Government		Non-U.S. Government		Total		U.S Government		Non-U.S. Government		Total
Product sales	$	568.8	$	334.7	$	903.5	$	526.1	$	80.4	$	606.5	$	374.8	$	46.7	$	421.5
Contract development and manufacturing services	—		80.0		80.0		—		98.9		98.9		—		68.9		68.9
Contracts and grants	105.9		16.6		122.5		71.5		5.5		77.0		65.1		5.4		70.5
Total revenues	$	674.7	$	431.3	$	1,106.0	$	597.6	$	184.8	$	782.4	$	439.9	$	121.0	$	560.9

Contract liabilities

When performance obligations are not transferred to a customer at the end of a reporting period, the amount allocated to those performance obligations are reflected as contract liabilities on the consolidated balance sheets and are deferred until control of these performance obligations is transferred to the customer. The following table presents the rollforward of contract liabilities:



(in millions)
December 31, 2017	$	30.5
Adoption of new accounting standard (ASC 606)	42.4
January 1, 2018	72.9
Deferral of revenue	29.3
Revenue recognized	(29.1		)
Balance at December 31, 2018	73.1
Deferral of revenue	46.7
Revenue recognized	(30.9		)
Balance at December 31, 2019	$	88.9

Transaction price allocated to remaining performance obligations

As of December 31, 2019, the Company had expected future revenues of approximately $600 million associated with performance obligations that have not been satisfied. The Company expects to recognize a majority of these revenues within the next 24 months, with the remainder recognized thereafter. However, the amount and timing of revenue recognition for unsatisfied performance obligations can materially change due to timing of funding appropriations from the USG and the overall success of the Company's development activities associated with its PHT product candidates that are then receiving development funding support from the USG under development contracts. In addition, the amount of future revenues associated with unsatisfied performance obligations excludes the value associated with unexercised option periods in the Company's contracts (which are not performance obligations as of December 31, 2019).

Contract assets

The Company considers unbilled accounts receivables and deferred costs associated with revenue generating contracts, which are not included in inventory or property, plant and equipments, as contract assets. As of December 31, 2019 and 2018, the Company had contract assets associated with deferred costs of $34.0 million and $1.2 million, respectively, which is included in prepaid expenses and other current assets and other assets on the Company's consolidated balance sheets.

Accounts receivable

Accounts receivable including unbilled accounts receivable contract assets consist of the following:



	December 31,
(in millions)	2019		2018
Billed, net	$	227.3	$	234.0
Unbilled	43.4		28.5
Total, net	$	270.7	$	262.5

As of December 31, 2019 and 2018, the Company's accounts receivable balances were comprised of 69% and 76%, respectively, from the USG. As of December 31, 2019 and 2018 allowance for doubtful accounts were de minimis.