Subsequent Events - Additional Information (Details) - USD ($) $ in Millions	Nov. 29, 2017	Nov. 27, 2017	Oct. 31, 2017	Jan. 31, 2017
Subsequent Event [Line Items]
Letters of credit facility			$ 26.5	$ 26.8
Subsequent Event
Subsequent Event [Line Items]
Decrease in restricted cash	$ 26.0
Subsequent Event | November 2017 Facility | Letters of Credit
Subsequent Event [Line Items]
Letters of credit facility	26.0
Subsequent Event | November 2017 Facility | Wells Fargo Bank | Secured Debt
Subsequent Event [Line Items]
Line of credit facility maturity date		Nov. 27, 2020
Subsequent Event | November 2017 Facility | Wells Fargo Bank | Secured Debt | Revolving Credit Facility
Subsequent Event [Line Items]
Line of credit facility, maximum borrowing capacity		$ 85.0
Line of credit facility, interest payment terms		Interest on the revolving loans is payable quarterly in arrears with respect to loans based on the prime rate and at the end of an interest period in the case of loans based on the LIBOR rate (or at each three month interval if the interest period is longer than three months).
Line of credit facility	40.0
Subsequent Event | November 2017 Facility | Wells Fargo Bank | Secured Debt | Revolving Credit Facility | Prime Rate
Subsequent Event [Line Items]
Line of credit facility, floating interest rate		0.25%
Subsequent Event | November 2017 Facility | Wells Fargo Bank | Secured Debt | Revolving Credit Facility | London Interbank Offered Rate (LIBOR)
Subsequent Event [Line Items]
Line of credit facility, floating interest rate		1.00%
Subsequent Event | November 2017 Facility | Wells Fargo Bank | Secured Debt | Letters of Credit
Subsequent Event [Line Items]
Line of credit facility, maximum borrowing capacity		$ 30.0
Line of credit facility, amount drawn	$ 26.0
Subsequent Event | December 2015 Facility | Secured Debt | Revolving Credit Facility
Subsequent Event [Line Items]
Repayment of outstanding principal balance		$ 40.0
Line of credit facility, termination date		Nov. 27, 2017