LONG-TERM DEBT (Tables)

12 Months Ended

Dec. 31, 2016

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

At December 31,	2016 Weighted- average Coupon(1)		2016			2015
(millions, except percentages)
Unsecured Senior and Medium-Term Notes:
2.98% to 7.20%, due 2017 to 2051	4.84	%	$	634.5		$	534.5
Total principal			634.5			534.5
Securities due within one year	6.85	%	(14.5		)	—
Debt issuance costs			(3.7		)	(3.3		)
Total long-term debt			$	616.3		$	531.2

(1) Represents weighted-average coupon rates for debt outstanding as of December 31, 2016.

Schedule of Maturities of Long-term Debt

Based on stated maturity dates , the scheduled principal payments of long-term debt at December 31, 2016, were as follows:

	2017			2018			2019		2020		2021		Thereafter			Total
(millions, except percentages)
Questar Gas	$	14.5		$	120.0		$	—	$	—	$	—	$	500.0		$	634.5
Weighted-average coupon	6.85		%	5.72		%							4.57		%