Balance Sheets Parenthetical - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Nuclear fuel; fuel in process	$ 73,105	$ 62,833
Allowance for Doubtful Accounts Receivable, Current	$ 1,514	$ 2,070
Common Stock, Par or Stated Value Per Share	$ 1	$ 1
Common Stock, Shares Authorized	100,000,000	100,000,000
Common Stock, Shares, Issued	65,678,261	65,707,156
Common stock, Restricted shares	150,427	121,532
Treasury Stock, Shares	25,090,505	25,147,567