Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Significant Accounting Policies [Abstract]

Schedule Of Allowance For Doubtful Accounts

Year Ended	Item	Balance at beginning of year		Additions charged to expense		Other		Balance at end of year
2017	Allowance for doubtful accounts	$	12,920	$	1,051	$	(3,713)	$	10,258
2016	Allowance for doubtful accounts		14,139		1,552		(2,771)		12,920
2015	Allowance for doubtful accounts		10,300		3,766		73		14,139