Subsequent Events - Narrative (Details)	Dec. 02, 2017 USD ($) ft² renewal_option	Dec. 01, 2017	Oct. 31, 2017 USD ($)	Jan. 31, 2017 USD ($)
Subsequent Event [Line Items]
Letters of credit issued and outstanding			$ 4,400,000	$ 5,400,000
Subsequent Event
Subsequent Event [Line Items]
Office lease, rentable square feet | ft²	207,066
Letters of credit issued and outstanding	$ 8,000,000
Phase One | Subsequent Event
Subsequent Event [Line Items]
Office lease, rentable square feet | ft²	19,060
Office lease, number of floors	1
Rent abatement (in months)	11 months
Phase Two | Subsequent Event
Subsequent Event [Line Items]
Office lease, rentable square feet | ft²	188,006
Office lease, number of floors	9
Phases One and Two | Subsequent Event
Subsequent Event [Line Items]
Total lease payments	$ 170,600,000
Annual lease payments for the first year	1,300,000
Annual lease payments for the second year	$ 8,700,000
Lease term	10 years
Number of renewal extensions | renewal_option	2
Renewal term	5 years
Phases One and Two | Leasehold Improvements | Subsequent Event
Subsequent Event [Line Items]
Tenant improvement allowance	$ 20,700,000
Phase Two, Year One | Subsequent Event
Subsequent Event [Line Items]
Rent abatement (in months)	8 months
Phase Two, Year Two | Subsequent Event
Subsequent Event [Line Items]
Rent abatement (in months)	5 months
Phase Three | Subsequent Event
Subsequent Event [Line Items]
Office lease, rentable square feet | ft²	47,939
Office lease, number of floors		2.5
Total lease payments	$ 35,600,000
Annual lease payments for the first year	$ 2,200,000
Rent abatement (in months)	5 months
Phase Three | Leasehold Improvements | Subsequent Event
Subsequent Event [Line Items]
Tenant improvement allowance	$ 4,000,000
Line of Credit | Subsequent Event
Subsequent Event [Line Items]
Line of credit maximum borrowing capacity	8,000,000.0
Line of Credit | Phase Three | Subsequent Event
Subsequent Event [Line Items]
Required increase to the letter of credit	$ 1,900,000