Commitments and Contingencies - Employee Contracts and Severance Costs (Details)	3 Months Ended
Mar. 31, 2019
Employment contracts
Restructuring Cost and Reserve [Line Items]
Maximum term of executive's annual base salary to determine severance obligations	12 months

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_RestructuringCostAndReserveLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration