Commitments and Contingencies - Rent Expense and Capitalized Costs (Details) - New Headquarters, New Haven, CT - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2018
Other Commitments [Line Items]
Rent expense	$ 4	$ 40
Capitalized costs	$ 1,114	$ 2,493

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

No definition available.

Name:	us-gaap_LeaseAndRentalExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration