Fair Value Measurements and Guarantees (Tables)
 3 Months Ended
Mar. 31, 2015
Fair Value Disclosures [Abstract]  
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]
 
 
 
 
 
Fair Value Measurements Using
 
 Carrying 
Amount
 
Fair
Value
 
Quoted
Prices In
Active
 Markets for 
Identical
Assets
(Level 1)
 
 Significant 
Other
Observable
Inputs
(Level 2)
 
Significant
Unobservable
Inputs
(Level 3)
 
(Millions)
Assets (liabilities) at March 31, 2015:
 
 
 
 
 
 
 
 
 
Measured on a recurring basis:
 
 
 
 
 
 
 
 
 
ARO Trust investments
$
60

 
$
60

 
$
60

 
$
—

 
$
—

Energy derivatives assets not designated as hedging instruments
2

 
2

 
—

 
—

 
2

Energy derivatives liabilities not designated as hedging instruments
(2
)
 
(2
)
 
—

 
—

 
(2
)
Additional disclosures:
 
 
 
 
 
 
 
 
 
Notes receivable and other
5

 
5

 
1

 
4

 
—

Long-term debt, including current portion (1)
(17,920
)
 
(18,318
)
 
—

 
(18,318
)
 
—

 
 
 
 
 
 
 
 
 
 
Assets (liabilities) at December 31, 2014:
 
 
 
 
 
 
 
 
 
Measured on a recurring basis:
 
 
 
 
 
 
 
 
 
ARO Trust investments
$
48

 
$
48

 
$
48

 
$
—

 
$
—

Energy derivatives assets not designated as hedging instruments
3

 
3

 
1

 
—

 
2

Energy derivatives liabilities not designated as hedging instruments
(2
)
 
(2
)
 
—

 
—

 
(2
)
Additional disclosures:
 
 
 
 
 
 
 
 
 
Notes receivable and other
5

 
4

 
—

 
4

 
—

Long-term debt, including current portion (1)
(16,325
)
 
(16,607
)
 
—

 
(16,607
)
 
—


 
(1) Excludes capital leases