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		$ 5,821	$ 4,911	$ 4,333
Charged to costs and expenses		3,947	4,431	3,988
Charged to other accounts	[1]	1,161	1,269	1,199
Deductions from reserves	[2]	5,801	4,790	4,609
Balance at Dec. 31		$ 5,128	$ 5,821	$ 4,911

[1] Recovery of amounts previously written off.

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