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
VALUATION AND QUALIFYING ACCOUNTS
Balance at Beginning of period	$ 43,757	$ 44,553	$ 23,545
Charged to Costs and Other Deductions	2,544	19,132	36,720
Charged to Other Accounts	86	(58)	(288)
Deductions	(2,011)	(19,870)	(15,424)
Balance at End of Period	44,376	43,757	44,553
Inventory reserve
VALUATION AND QUALIFYING ACCOUNTS
Balance at Beginning of period	26,537	46,813	45,141
Charged to Costs and Other Deductions	5,897	13,587	9,485
Deductions	(3,500)	(33,863)	(7,813)
Balance at End of Period	28,934	26,537	46,813
Valuation allowance on deferred tax assets
VALUATION AND QUALIFYING ACCOUNTS
Balance at Beginning of period	1,807,728	1,560,162	1,537,507
Charged to Other Accounts	61,762	247,566	22,655
Balance at End of Period	$ 1,869,490	$ 1,807,728	$ 1,560,162