Balance Sheets Parenthetical - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Nuclear fuel; fuel in process	$ 64,292	$ 51,854
Allowance for Doubtful Accounts Receivable, Current	$ 2,260	$ 2,046
Common Stock, Par or Stated Value Per Share	$ 1	$ 1
Common Stock, Shares Authorized	100,000,000	100,000,000
Common Stock, Shares, Issued	65,671,235	65,709,819
Common stock, restricted shares	156,976	118,834
Treasury Stock, Shares	25,305,965	25,384,834