Schedule II, Valuation and Qualifying Accounts (Details) - Allowance for Bad Debts - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Jan. 1		$ 23,122	$ 22,505	$ 21,918
Charged to costs and expenses		13,052	17,005	16,784
Charged to other accounts	[1]	5,175	6,240	7,005
Deductions from reserves	[2]	21,227	22,628	23,202
Balance at Dec. 31		$ 20,122	$ 23,122	$ 22,505

[1] Recovery of amounts previously written off.

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