Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for uncollectible accounts
Balance at the beginning of the period	$ 19,846	$ 17,702	$ 16,546
Additions Charged to Costs and Expenses	8,401	6,248	7,360
Additions Charged to Other Accounts	0	0	0
Write-offs	(6,098)	(6,129)	(6,325)
Other	(374)	2,025	121
Balance at the End of the period	$ 21,775	$ 19,846	$ 17,702