SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for doubtful accounts receivable and revenue adjustments
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	$ 4,825	$ 5,731	$ 4,533
Additions, Charged to Costs and Expenses	1,643	998	1,941
Additions, Charged to Other Accounts	980	(144)	2,363
Deductions	2,011	1,760	3,106
Balance at End of Period	5,437	4,825	5,731
Allowance for other accounts receivable
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	1,029	1,701	1,422
Additions, Charged to Costs and Expenses	(180)	(672)	279
Balance at End of Period	849	1,029	1,701
Allowance for deferred tax assets
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	354	332	1,028
Additions, Charged to Costs and Expenses		22
Deductions	61		696
Balance at End of Period	$ 293	$ 354	$ 332