Leases - Additional Information (Details) ft² in Thousands	1 Months Ended
	Jan. 31, 2012 USD ($) ft² Option	Mar. 31, 2019 USD ($)	Dec. 31, 2017 USD ($) ft²
Leases [Abstract]
Leased office space | ft²	66		44
Term of lease agreement	120 months
Number of options to extend lease | Option	2
Renewal term	5 years
Option to early terminate, period	5 years
Tenant improvements allowance	$ 3,900,000
Sublease payments receivable within five months			$ 0
Remaining scheduled sublease payments		$ 4,400,000