Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Condensed Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts, accounts receivable	$ 69	$ 1,733
Accumulated Depreciation Depletion And Amortization Property Plant And Equipment	$ 464,244	$ 460,708
Preferred shares, par value		$ 0.10
Preferred shares, shares authorized	5,000	5,000
Preferred shares, issued
Common stock, par value		$ 0.10
Common stock, shares authorized	145,000	145,000
Common stock, issued	37,679	41,357
Common stock, outstanding	37,679	41,357