Recently Issued Accounting Pronouncements- Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in net cash from operating activities	$ 23,494	$ 38,396
ASU 2016-18 [Member]
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in net cash from operating activities	$ (14,400)		$ 14,400