Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Movement in Valuation Allowances and Reserves [Roll Forward]
Allowance for Doubtful Accounts, Balance at beginning of year		$ 56,291	$ 52,256	$ 49,659
Allowance for doubtful accounts, Charged to Income		34,936	12,887	8,336
Valuation Allowances and Reserves, Additions for Charges to Other Accounts	[1]	(1,958)	2,831	(392)
Allowance for Doubtful Accounts, Write-down		13,681	11,683	5,347
Allowance for Doubtful Accounts, Balance at end of year		$ 75,588	$ 56,291	$ 52,256

[1] "Other" primarily includes the effect of fluctuations in foreign currencies and the allowance for doubtful accounts of the businesses acquired by the company.