Regulatory Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2014

Regulatory Assets and Liabilities Disclosure [Abstract]

Schedule of Regulatory Assets And Liabilities

	Note Reference	Remaining Amortization Period	December 31,
			2014		2013
			(in thousands)
Pension	16	Undetermined	$	139,050	$	58,474
Employee related benefits	16	Undetermined	19,080		17,700
Distribution infrastructure projects		3 Years	9,407		12,543
Environmental clean-up	20	Various	13,741		14,924
Supply costs		1 Year	29,200		17,875
Income taxes	13	Plant Lives	263,764		201,808
Deferred financing costs		Various	12,151		13,919
State & local taxes & fees		Various	5,319		6,582
Other	—	Various	11,419		10,846
Total regulatory assets			$	503,131	$	354,671
Removal cost	7	Various	$	351,676	$	336,613
Gas storage sales		25 Years	10,410		10,831
Supply costs		1 Year	14,569		11,493
Deferred revenue	4	1 Year	36,592		33,400
Environmental clean-up		Various	2,501		1,194
State & local taxes & fees		1 Year	511		551
Other		Various	2,138		377
Total regulatory liabilities			$	418,397	$	394,459