Commitments, Guarantees and Contingencies - Additional Information (Details) - USD ($) $ in Thousands		6 Months Ended
	May 10, 2018	Sep. 30, 2018	Mar. 31, 2018
Disclosure Of Commitments And Contingencies [Line Items]
Applicable program documentation period		365 days
Accrual preliminary settlement litigation amount			$ 19,000
Federal Securities Class Action
Disclosure Of Commitments And Contingencies [Line Items]
Amount payable under settlement agreement	$ 19,000
Accrual preliminary settlement litigation amount		$ 19,000