Regulatory Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2019

Regulatory Assets and Liabilities Disclosure [Abstract]

Schedule of Regulatory Assets And Liabilities

	Note Reference	Remaining Amortization Period	December 31,
			2019		2018
			(in thousands)
Income taxes	12	Plant Lives	$	277,434	$	230,434
Pension	14	Undetermined	132,000		130,193
Deferred financing costs		Various	31,089		34,080
Employee related benefits	14	Undetermined	18,622		19,458
Supply costs		1 Year	35,454		10,532
State & local taxes & fees		Various	7,146		15,532
Environmental clean-up	18	Various	11,179		11,221
Other		Various	25,639		24,562
Total Regulatory Assets			$	538,563	$	476,012
Removal cost	6	Various	$	442,129	$	428,528
Tax Cut and Jobs Act		1 Year	—		20,497
Supply costs		1 Year	14,226		15,453
Gas storage sales		20 Years	8,307		8,728
Rates subject to refund		1 Year	14,177		—
State & local taxes & fees		1 Year	1,846		1,747
Environmental clean-up		Various	1,181		1,247
Other		Various	2,697		2,961
Total Regulatory Liabilities			$	484,563	$	479,161