XML 30 R76.htm IDEA: XBRL DOCUMENT v2.4.0.8
Long-Term Debt and Capital Leases Schedule of Long-Term Debt (Details) (Secured Debt, USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2013
Secured Debt Montana and South Dakota due in 2028 and 2043 [Member]
  
Debt Instrument [Line Items]  
Debt instrument, issuance date Dec. 19, 2013
Secured Debt Montana and South Dakota due 2043 [Member]
  
Debt Instrument [Line Items]  
Debt instrument, face amount $ 65
Interest rate, stated percentage 4.85%
Maturity date Dec. 19, 2043
Secured Debt Montana Due 2028 [Member]
  
Debt Instrument [Line Items]  
Debt instrument, face amount $ 35
Interest rate, stated percentage 3.99%
Maturity date Dec. 19, 2028