Significant Accounting Policies (Schedule of Allowance for Doubtful Accounts) (Details) - Allowance for doubtful accounts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 10,258	$ 12,920	$ 14,139
Additions charged to expense	1,824	1,051	1,552
Other	(3,659)	(3,713)	(2,771)
Balance at end of year	$ 8,423	$ 10,258	$ 12,920