Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Assets
Property, plant and equipment, at cost	$ 13,111,170	$ 12,610,376
Less: accumulated depreciation	2,518,805	2,358,510
Net property, plant and equipment	10,592,365	10,251,866
Current assets:
Cash and cash equivalents	12,976	10,567
Accounts receivable, net	143,385	141,025
Unbilled revenues	79,394	119,896
Inventory - materials and supplies	38,193	33,756
Inventory - gas stored	90,417	75,804
Prepayments and other current assets	31,722	36,597
Regulatory assets	17,208	20,150
Total current assets	413,295	437,795
Regulatory assets	1,511,541	1,429,840
Deferred charges and other assets, net	136,764	141,955
Funds restricted for construction activity	1,313	1,313
Goodwill	2,340,792	2,340,815
Operating lease right-of-use assets	44,713	48,930
Intangible assets	5,381	5,764
Total assets	15,046,164	14,658,278
Stockholders' equity:
Common stock at $0.50 par value, authorized 600,000,000 shares, issued 265,415,337 and 256,102,388 as of June 30, 2022 and December 31, 2021	132,707	128,050
Capital in excess of par value	3,715,975	3,705,814
Retained earnings	1,577,442	1,434,201
Treasury stock, at cost, 3,244,664 and 3,234,765 shares as of June 30, 2022 and December 31, 2021	(84,092)	(83,615)
Total stockholders' equity	5,342,032	5,184,450
Long-term debt, excluding current portion	6,135,390	5,815,211
Less: debt issuance costs	47,654	35,707
Long-term debt, excluding current portion, net of debt issuance costs	6,087,736	5,779,504
Commitments and contingencies (See Note 13)
Current liabilities:
Current portion of long-term debt	120,931	132,146
Loans payable	4,703	65,000
Accounts payable	194,105	192,932
Book overdraft	20,659	81,722
Accrued interest	43,384	40,815
Accrued taxes	34,457	37,924
Regulatory liabilities	1,878	384
Other accrued liabilities	124,008	124,140
Total current liabilities	544,125	675,063
Deferred credits and other liabilities:
Deferred income taxes and investment tax credits	1,511,182	1,406,537
Customers' advances for construction	109,457	103,619
Regulatory liabilities	755,651	769,617
Asset retirement obligations	1,268	1,256
Operating lease liabilities	41,736	48,230
Pension and other postretirement benefit liabilities	28,698	50,226
Other	28,328	43,666
Total deferred credits and other liabilities	2,476,320	2,423,151
Contributions in aid of construction	595,951	596,110
Total liabilities and equity	$ 15,046,164	$ 14,658,278