Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets
Property, plant and equipment, at cost	$ 12,836,605	$ 12,610,376
Less: accumulated depreciation	2,441,921	2,358,510
Net property, plant and equipment	10,394,684	10,251,866
Current assets:
Cash and cash equivalents	58,298	10,567
Accounts receivable, net	182,587	141,025
Unbilled revenues	104,540	119,896
Inventory - materials and supplies	38,560	33,756
Inventory - gas stored	20,502	75,804
Prepayments and other current assets	29,856	36,597
Regulatory assets	9,172	20,150
Total current assets	443,515	437,795
Regulatory assets	1,505,211	1,429,840
Deferred charges and other assets, net	139,608	141,955
Funds restricted for construction activity	1,313	1,313
Goodwill	2,340,815	2,340,815
Operating lease right-of-use assets	46,305	48,930
Intangible assets	5,572	5,764
Total assets	14,877,023	14,658,278
Stockholders' equity:
Common stock at $0.50 par value, authorized 600,000,000 shares, issued 256,281,789 and 256,102,388 as of March 31, 2022 and December 31, 2021	128,140	128,050
Capital in excess of par value	3,713,560	3,705,814
Retained earnings	1,497,757	1,434,201
Treasury stock, at cost, 3,250,261 and 3,234,765 shares as of March 31, 2022 and December 31, 2021	(84,357)	(83,615)
Total stockholders' equity	5,255,100	5,184,450
Long-term debt, excluding current portion	5,910,363	5,815,211
Less: debt issuance costs	38,403	35,707
Long-term debt, excluding current portion, net of debt issuance costs	5,871,960	5,779,504
Commitments and contingencies (See Note 13)
Current liabilities:
Current portion of long-term debt	131,746	132,146
Loans payable	79,743	65,000
Accounts payable	161,511	192,932
Book overdraft		81,722
Accrued interest	66,133	40,815
Accrued taxes	37,130	37,924
Regulatory liabilities	17,241	384
Dividends payable	67,863
Other accrued liabilities	116,811	124,140
Total current liabilities	678,178	675,063
Deferred credits and other liabilities:
Deferred income taxes and investment tax credits	1,481,253	1,406,537
Customers' advances for construction	104,403	103,619
Regulatory liabilities	759,661	769,617
Asset retirement obligations	1,262	1,256
Operating lease liabilities	43,946	48,230
Pension and other postretirement benefit liabilities	48,864	50,226
Other	35,998	43,666
Total deferred credits and other liabilities	2,475,387	2,423,151
Contributions in aid of construction	596,398	596,110
Total liabilities and equity	$ 14,877,023	$ 14,658,278