Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deposits in trusts for employee deferred compensation plans	$ 311,708	$ 292,326
Other	90,877	112,385
Other current assets	$ 402,585	$ 404,711