XML 53 R52.htm IDEA: XBRL DOCUMENT v2.4.0.8
Fair Value Measurements (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2013
Carrying Amount [Member]
Dec. 31, 2012
Carrying Amount [Member]
Dec. 31, 2013
Estimated Fair Value [Member]
Level 1 [Member]
Dec. 31, 2012
Estimated Fair Value [Member]
Level 1 [Member]
Dec. 31, 2013
Estimated Fair Value [Member]
Level 2 [Member]
Dec. 31, 2012
Estimated Fair Value [Member]
Level 2 [Member]
Dec. 31, 2013
Questar Gas [Member]
Carrying Amount [Member]
Dec. 31, 2012
Questar Gas [Member]
Carrying Amount [Member]
Dec. 31, 2013
Questar Gas [Member]
Estimated Fair Value [Member]
Level 1 [Member]
Dec. 31, 2012
Questar Gas [Member]
Estimated Fair Value [Member]
Level 1 [Member]
Dec. 31, 2013
Questar Gas [Member]
Estimated Fair Value [Member]
Level 2 [Member]
Dec. 31, 2012
Questar Gas [Member]
Estimated Fair Value [Member]
Level 2 [Member]
Sep. 30, 2013
Questar Pipeline [Member]
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Inputs, Level 3 [Member]
Dec. 31, 2013
Questar Pipeline [Member]
Carrying Amount [Member]
Dec. 31, 2012
Questar Pipeline [Member]
Carrying Amount [Member]
Dec. 31, 2013
Questar Pipeline [Member]
Estimated Fair Value [Member]
Level 1 [Member]
Dec. 31, 2012
Questar Pipeline [Member]
Estimated Fair Value [Member]
Level 1 [Member]
Dec. 31, 2013
Questar Pipeline [Member]
Estimated Fair Value [Member]
Level 2 [Member]
Dec. 31, 2012
Questar Pipeline [Member]
Estimated Fair Value [Member]
Level 2 [Member]
Financial assets [Abstract]                                      
Cash and cash equivalents $ 16.0 $ 16.8 $ 16.0 $ 16.8     $ 8.8 $ 1.4 $ 8.8 $ 1.4       $ 2.7 $ 7.1 $ 2.7 $ 7.1    
Long-term investment 17.3 15.5 17.3 15.5                              
Notes receivable from Questar                           29.4 38.7 29.4 38.7    
Financial liabilities [Abstract]                                      
Short-term debt 276.0 263.0 276.0 263.0                              
Notes payable to Questar             17.7 166.1 17.7 166.1                  
Long-term debt, including current portion 1,247.1 1,140.9     1,310.8 1,303.1 534.5 426.5     568.0 503.7   458.9 458.9     486.0 536.6
Property, Plant, and Equipment, Fair Value Disclosure                         $ 0