Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Property, plant, and equipment, accumulated depreciation	$ 32,801	$ 31,588
Leased property, net of accumulated depreciation	16,394	11,812
Intangible assets, net of accumulated amortization	$ 2,036	$ 1,735
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized	750,000,000	750,000,000
Common Stock, shares issued	229,655,825	229,073,517
Common stock in treasury, shares	15,002,663	587,151
Series C Redeemable Convertible Preferred Stock
Redeemable convertible Preferred Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Redeemable convertible Preferred Stock, shares authorized	10,431	10,431
Redeemable convertible Preferred Stock, shares issued	2,620	2,620
Redeemable convertible Preferred Stock, shares outstanding	2,620	2,620
Redeemable convertible Preferred Stock, aggregate involuntary liquidation preference (in dollars)	$ 16,664	$ 16,664

Cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land or leased assets).

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