Revenue recognition

6 Months Ended

Jun. 30, 2019

Revenue from Contract with Customer [Abstract]

The Company operates as one operating segment. Therefore, results of its operations are reported on a consolidated basis for purposes of segment reporting, consistent with internal management reporting. The Company's revenues disaggregated by the major sources were as follows:



	Three Months Ended June 30, 2019						Three Months Ended June 30, 2018
	U.S. Government		Non-U.S. Government		Total		U.S. Government		Non-U.S. Government		Total
Product sales	$	94.6	$	88.9	$	183.5	$	169.9	$	10.2	$	180.1
Contract manufacturing	—		18.7		18.7		—		23.6		23.6
Contracts and grants	38.3		2.7		41.0		15.3		1.2		16.5
Total revenues	$	132.9	$	110.3	$	243.2	$	185.2	$	35.0	$	220.2



	Six months ended June 30, 2019						Six Months Ended June 30, 2018
	U.S. Government		Non-U.S. Government		Total		U.S. Government		Non-U.S. Government		Total
Product sales	$	167.9	$	168.6	$	336.5	$	235.9	$	19.9	$	255.8
Contract manufacturing	—		34.6		34.6		—		49.8		49.8
Contracts and grants	58.7		4.1		62.8		30.1		2.3		32.4
Total revenues	$	226.6	$	207.3	$	433.9	$	266.0	$	72.0	$	338.0

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 is reflected as deferred revenue on the consolidated balance sheets and is deferred until control of these performance obligations is transferred to the customer. The following table presents the rollforward of deferred revenue contract liability balances:




December 31, 2018	$	73.1
Deferral of revenue	23.8
Revenue recognized	(7.4		)
June 30, 2019	$	89.5

Transaction price allocated to remaining performance obligations

As of June 30, 2019, the Company had expected future revenues associated with performance obligations that have not been satisfied of approximately $533.2 million. 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.

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 equipment, as contract assets. As of June 30, 2019 and December 31, 2018, the Company had contract assets associated with deferred costs of $26.5 million and $1.2 million, respectively, which is reflected as a component of prepaid expenses and other current assets on the Company's consolidated balance sheets.

Accounts receivable

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



	June 30, 2019		December 31, 2018
Billed, net	$	179.5	$	234.0
Unbilled	38.6		28.5
Total, net	$	218.1	$	262.5

As of June 30, 2019 and December 31, 2018, allowances for doubtful accounts were de minimis.