Revenue Recognition - Schedule of Changes in Contract Balances Due to Adoption of New Accounting Standards (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Revenue From Contract With Customer Balances Of Net Contract Assets Liabilities [Line Items]
Contract assets	$ 143,161	$ 123,197
Contract liabilities	(26,489)	(38,571)
Net contract assets (liabilities)	116,672
ASU 2014-09 | As Reported
Revenue From Contract With Customer Balances Of Net Contract Assets Liabilities [Line Items]
Contract assets	141,391	123,197
Contract liabilities	(27,009)	(38,571)
Net contract assets (liabilities)		$ 84,626
ASU 2014-09 | Change
Revenue From Contract With Customer Balances Of Net Contract Assets Liabilities [Line Items]
Contract assets	19,964
Contract liabilities	12,082
Net contract assets (liabilities)	$ 32,046