Commitments and Contingencies (Details) $ in Thousands		9 Months Ended
	Jan. 05, 2018 ft² option building	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Proceeds from sale of Summers Ridge Property		$ 146,644	$ 0
Initial lease term	15 years
Number of buildings leased | building	2
Number of buildings in the property | building	4
Area of leased property (in square feet) | ft²	124,461
Number of options to extend | option	2
Renewal term	5 years
Future minimum lease payments, remainder of 2018		1,500
Future minimum lease payments, 2019		6,500
Future minimum lease payments, 2020		7,600
Future minimum lease payments, 2021		7,800
Future minimum lease payments, 2022		8,000
Future minimum lease payments, 2023		8,300
Future minimum lease payments, after 2023		$ 86,800