Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for doubtful accounts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation and Qualifying Accounts
Balance at Beginning of Period	$ 3,315	$ 2,549	$ 2,546
Charged to Cost and Expenses	764	985	1,136
Charged to Other Accounts	0	0	0
Deductions, Actual Charge-Offs	(991)	(219)	(1,133)
Balance at End of Period	$ 3,088	$ 3,315	$ 2,549