Schedule II Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts Receivable [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance beginning of period	$ 7,889	$ 6,853	$ 5,514
Additions charged to revenues, costs, expenses	8,090	2,400	2,678
Deductions amounts charged off-net	3,410	1,364	1,339
Balance end of period	$ 12,569	$ 7,889	$ 6,853