SCHEDULE II. VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances, beginning balance		$ 10,424	$ 18,456	$ 22,675
Valuation allowances, charged to expenses		5,116	1,829	5,514
Valuation allowances, charged to other accounts	[1]	(3,107)	250	(4)
Valuation allowances, deductions	[2]	1,854	10,111	9,729
Valuation allowances, ending balance		10,579	10,424	18,456
Valuation Allowance of Deferred Tax Assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances, beginning balance		3,467	3,558	3,115
Valuation allowances, charged to expenses		42,816	228	674
Valuation allowances, charged to other accounts		0	0	0
Valuation allowances, deductions		0	319	231
Valuation allowances, ending balance		$ 46,283	$ 3,467	$ 3,558

[1] For allowance for doubtful accounts, primarily includes amounts previously written off which were credited directly to this account when recovered.

[2] For allowance for doubtful accounts, amounts written off as uncollectible or transferred to other accounts or utilized.