Leases - Summary of Total Lease Costs and Other Information (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2020
Lease cost:
Operating lease cost	$ 6,333	$ 12,932
Short-term lease cost	240	432
Variable lease cost	1,129	2,139
Total lease cost	7,702	15,503
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	6,244	12,625
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 5,426	$ 9,436