Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deposits in trusts for employee deferred compensation plans	$ 315,375	$ 292,326
Other	78,223	112,385
Other current assets	$ 393,598	$ 404,711