Derivative Instruments and Hedging Activities (Tables)

9 Months Ended

Sep. 30, 2011

Derivative Instruments and Hedging Activities [Abstract]

Derivative instruments on Consolidated Statements of Income and Accumulated Other Comprehensive Income

The following table presents the pre-tax effects of the derivative instrument designated as a fair value hedge (including the hedged item) on the Consolidated Statements of Income and the derivative instruments designated as cash flow hedges on AOCI:

	Financial Statement	3 Months Ended,	9 Months Ended,	12 Months Ended,
Instrument and Activity	Location of Gain (Loss)	Sept. 30, 2011
Fair Value Hedge
Questar Corporation
Interest rate derivative instrument
Realized and unrealized gain	Interest expense	$  5.2	$  9.1	$  9.1
2.75% notes due 2016
Realized and unrealized loss	Interest expense	(5.2)	(9.1)	(9.1)
Cash Flow Hedges
Questar Pipeline
Interest rate derivative instruments
Deferrals of effective portions	AOCI	($37.0)	($36.2)	($36.2)

Derivative instruments in Condensed Consolidated Balance Sheets

The following table discloses the Level 2 fair values of the asset and liability derivative instruments designated as hedges in the Condensed Consolidated Balance Sheets.

Instrument	Balance Sheet Location	Sept. 30, 2011
		(in millions)
Assets
Questar Corporation
Interest rate derivative instrument	Prepaid expenses and other	$  0.5
Interest rate derivative instrument	Other noncurrent assets	7.7
Consolidated total - derivative assets		$  8.2
Liabilities
Questar Pipeline
Interest rate derivative instruments	Accounts payable and accrued expenses	$  36.2
Consolidated total - derivative liabilities		$  36.2

Information about derivative instruments

The following table provides additional information about the Company's derivative instruments:

Instrument Type	Accounting Treatment	Maturity Date	Weighted-average Fixed Interest Rate1	Notional Amount
				(in millions)
Questar Corporation
Interest rate swap – pay floating, receive fixed	Fair Value Hedge	2016	2.75%	$  125.0
Questar Pipeline
Forward starting interest rate swaps – pay fixed, receive floating	Cash Flow Hedge	2011	3.91%	$  150.0