Condensed Consolidated Financial Statements - Narrative (Details) course in Millions, $ in Millions		6 Months Ended		12 Months Ended
	Dec. 22, 2016 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2017 USD ($) course	Dec. 31, 2016 USD ($) course
Procurement Contract [Line Items]
Payments for legal settlements	$ 217.0
Reduced holdback amount				$ 40.9
BARDA Contract
Procurement Contract [Line Items]
Government contract, total number of courses required to be delivered | course			2.0	2.0
Reduced holdback amount			$ 41.0
Forecast | BARDA Contract
Procurement Contract [Line Items]
Reduced holdback amount		$ 41.0