Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts [Member] - 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 beginning of period	$ 10,017	$ 9,939	$ 10,528
Charged to costs and expenses	692	206	15
Write-offs (recoveries) of doubtful accounts	411	128	604
Balance at end of period	$ 10,298	$ 10,017	$ 9,939