Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Current assets:
Cash and cash equivalents	$ 66,070	$ 66,459	$ 67,000
Receivables, net	1,009,433	836,605	968,279
Inventories	286,223	278,407	286,057
Current regulatory assets	79,125	63,613	69,181
Prepayments and other current assets	61,706	52,617	71,298
Total current assets	1,502,557	1,297,701	1,461,815
Noncurrent assets:
Property, plant and equipment	8,203,751	7,908,628	7,746,754
Less accumulated depreciation, depletion and amortization	3,115,805	2,991,486	2,944,928
Net property, plant and equipment	5,087,946	4,917,142	4,801,826
Goodwill	712,677	681,358	681,349
Other intangible assets, net	26,376	15,246	15,511
Regulatory assets	369,764	353,784	362,799
Investments	158,440	148,656	144,417
Operating lease right-of-use assets	120,534	115,323	118,764
Other	147,205	153,849	144,130
Total noncurrent assets	6,622,942	6,385,358	6,268,796
Total assets	8,125,499	7,683,059	7,730,611
Current liabilities:
Short-term borrowings	75,000	0	139,988
Long-term debt due within one year	1,558	16,540	65,810
Accounts payable	436,718	403,391	378,370
Taxes payable	96,708	48,970	53,505
Dividends payable	41,608	41,580	40,460
Accrued compensation	110,730	99,269	93,642
Regulatory liabilities due within one year	39,837	42,935	36,945
Operating lease liabilities due within one year	33,770	31,664	32,584
Asset retirement obligations due within one year	4,198	4,277	5,612
Other accrued liabilities	226,863	177,801	186,761
Total current liabilities	1,066,990	866,427	1,033,677
Noncurrent liabilities:
Long-term debt	2,268,732	2,226,567	2,180,946
Deferred income taxes	533,524	506,583	487,194
Regulatory liabilities	434,936	447,370	453,760
Asset retirement obligations	425,567	413,298	384,193
Operating lease liabilities	87,140	83,742	86,166
Other	295,845	291,826	309,069
Total noncurrent liabilities	4,045,744	3,969,386	3,901,328
Commitments and contingencies
Stockholders' equity:
Common stock	201,061	200,923	200,876
Other paid-in capital	1,366,494	1,355,404	1,351,990
Retained earnings	1,489,085	1,336,647	1,283,044
Accumulated other comprehensive loss	(40,249)	(42,102)	(36,678)
Treasury stock at cost - 538,921 shares	(3,626)	(3,626)	(3,626)
Total stockholders' equity	3,012,765	2,847,246	2,795,606
Total liabilities and stockholders' equity	$ 8,125,499	$ 7,683,059	$ 7,730,611
Common Stock, Shares Authorized	500,000,000	500,000,000	500,000,000
Common Stock, Par or Stated Value Per Share	$ 1.00	$ 1.00	$ 1.00
Common Stock, Shares, Issued	201,061,198	200,922,790	200,876,334
Treasury Stock, Common, Shares	538,921	538,921	538,921