|
Derivatives and Hedging (Details) (USD $)
|
3 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|
|
Mar. 31, 2015
|
Dec. 31, 2011
|
Dec. 31, 2014
|
Dec. 31, 2011
|
Mar. 31, 2014
|
|
| Derivative [Line Items] | |||||
| Derivative Assets (Liabilities), at Fair Value, Net | $ 0 | 0 | $ 0 | ||
| Cash Flow Hedging [Member] | Questar Pipeline [Member] | Forward Starting Interest Rate Swaps Terminating Q4 2011 [Member] | |||||
| Derivative [Line Items] | |||||
| Notional amount | 150,000,000 | 150,000,000 | |||
| Debt Instrument, Face Amount | 180,000,000 | 180,000,000 | |||
| Interest payment for terminated derivative instrument | 37,300,000 | ||||
| Life of long-term debt associated with cash flow hedges | 30 years | ||||
| Date Through Which Reclassifications Into Earnings From AOCI Will Take Place | 2041 | ||||
| Pre-tax net losses expected to be reclassified from AOCI to Consolidated statement of income | $ 600,000 | ||||
| Reclassification from accumulated OCI to income, time to transfer | 12 months | ||||