Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowances for doubtful accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 4,919	$ 7,633	$ 7,222
Charged (Credited) to Costs and Expenses	1,834	1,841	7,275
Deductions	(5,310)	(4,555)	(6,864)
Balance at End of Year	1,443	4,919	7,633
Allowances for doubtful notes receivable [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	4,000	4,000	0
Charged (Credited) to Costs and Expenses	0	0	4,000
Deductions	0	0	0
Balance at End of Year	4,000	4,000	4,000
Warranty [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	124	399	643
Charged (Credited) to Costs and Expenses	37	13	381
Deductions	(99)	(288)	(625)
Balance at End of Year	62	124	399
Valuation allowance on deferred tax assets [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	194,255	205,264	151,035
Charged (Credited) to Costs and Expenses	23,334	(11,009)	54,229
Deductions	0	0	0
Balance at End of Year	217,589	194,255	205,264
Excess and obsolete inventory [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	24,475	29,804	32,555
Charged (Credited) to Costs and Expenses	429	151	6,952
Deductions	(9,855)	(5,480)	(9,703)
Balance at End of Year	$ 15,049	$ 24,475	$ 29,804