Condensed Consolidated Balance Sheets Parenthetical - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Other property and equipment, accumulated depreciation	$ 59,720	$ 57,102
Common Stock, par value per share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	200,000,000	200,000,000
Common Stock, Shares, Issued	112,244,545	112,241,966
Common Stock, Shares, Outstanding	112,244,545	112,241,966