XML 104 R66.htm IDEA: XBRL DOCUMENT v3.10.0.1
Investments and Restricted Cash and Investments (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Investments And Restricted Cash And Investments [Line Items]          
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification     $ 0    
Investments [Abstract]          
Investments $ 1,937   1,937   $ 2,526
Equity Method Investments [Abstract]          
Equity method investments 1,967   1,967   1,834
Restricted Cash and Investments [Abstract]          
Restricted cash and investments 842   842   863
Investments, including equity method investments and restricted cash and investments 4,746   4,746   5,223
Investments, including equity method investments and restricted cash and investments, current 342   342   351
Investments, including equity method investments and restricted cash and investments, noncurrent 4,404   4,404   4,872
Gain on Sale of Investments (387) $ 2 (596) $ 5  
Marketable Securities, Realized Gain (Loss) (1)   1    
Marketable Securities, Gain (Loss) (386)   (597)    
Quad Cities Station nuclear decommissioning trust funds [Member]          
Restricted Cash and Investments [Abstract]          
Decommissioning fund investments, fair value 522   522   515
Other restricted cash and investments [Member]          
Restricted Cash and Investments [Abstract]          
Restricted cash and investments 320   320   348
Equity Method Investments, tax equity investments [Member]          
Equity Method Investments [Abstract]          
Equity method investments 1,159   1,159   1,025
ETT [Member]          
Equity Method Investments [Abstract]          
Equity method investments 535   535   524
Bridger Coal Company [Member]          
Equity Method Investments [Abstract]          
Equity method investments 124   124   137
Other equity method investments [Member]          
Equity Method Investments [Abstract]          
Equity method investments 149   149   148
BYD Company Limited common stock [Member]          
Investments [Abstract]          
Available-for-sale securities, equity securities 1,364   1,364   1,961
Rabbi trusts [Member]          
Investments [Abstract]          
Rabbi trusts, amount 387   387   441
Other investments [Member]          
Investments [Abstract]          
Other investments $ 186   186   $ 124
Retained Earnings [Member]          
Investments And Restricted Cash And Investments [Line Items]          
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification     $ 1,085