SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts receivable and revenue adjustments
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	$ 5,437	$ 4,825	$ 5,731
Additions, Charged to Costs and Expenses	4,081	1,643	998
Additions, Charged to Other Accounts	2,416	980	(144)
Deductions	4,277	2,011	1,760
Balance at End of Period	7,657	5,437	4,825
Allowance for other accounts receivable
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	849	1,029	1,701
Additions, Charged to Costs and Expenses	72	(180)	(672)
Balance at End of Period	921	849	1,029
Allowance for deferred tax assets
Changes in valuation and qualifying accounts and reserves
Balance at Beginning of Period	293	354	332
Additions, Charged to Costs and Expenses			22
Deductions	(551)	61
Balance at End of Period	$ 844	$ 293	$ 354

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

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- Definition

Amount of increase in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, from charges to costs and expenses.

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- Definition

+ References

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- Definition

Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.

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