Summary of Significant Accounting Policies - Summary of Lease Exit Accruals (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Accounting Policies [Abstract]
Beginning balance	$ 9,790
Lease exit expense	2,016
Payments	(2,671)
Other	(1,377)
Ending balance	$ 7,758