Consolidated Balance Sheets $ in Thousands		12 Months Ended
		Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Property, Plant and Equipment:
Utility Plant, at original cost		$ 2,211,239	$ 2,002,966
Accumulated Depreciation		(440,473)	(413,597)
Nonutility Property and Equipment, at cost		785,646	622,079
Accumulated Depreciation		(108,307)	(77,345)
Property, Plant and Equipment - Net		2,448,105	2,134,103
Investments:
Available-for-Sale Securities		14,810	8,922
Restricted Investments		48,758	65,451
Investment in Affiliates		16,983	68,351
Total Investments		80,551	142,724
Current Assets:
Cash and Cash Equivalents		3,877	4,171
Accounts Receivable		178,359	251,892
Unbilled Revenues		40,044	62,608
Provision for Uncollectibles		(10,252)	(7,910)
Notes Receivable		11,800	0
Notes Receivable - Affiliate		3,134	14,657
Natural Gas in Storage, average cost		54,211	63,246
Materials and Supplies, average cost		5,088	2,125
Deferred Income Taxes - Net		0	57,748
Prepaid Taxes		21,753	14,106
Derivatives - Energy Related Assets		83,093	85,368
Other Prepayments and Current Assets		40,167	18,686
Total Current Assets		431,274	566,697
Regulatory and Other Noncurrent Assets:
Regulatory Assets		323,434	357,160
Derivatives - Energy Related Assets		16,238	13,905
Unamortized Debt Issuance Costs		8,967	9,795
Notes Receivable - Affiliate		13,275	36,799
Contract Receivables		28,609	19,236
Notes Receivable		35,439	7,882
Goodwill		8,880	0
Identifiable Intangible Assets		21,553	0
Other		64,575	61,124
Total Regulatory and Other Noncurrent Assets		520,970	505,901
Total Assets		3,480,900	3,349,425
Common Stock: Par Value $1.25 per share; Authorized 120,000,000 shares; Outstanding Shares: 70,965,622 (2015) and 68,334,860 (2014)
Balance at Beginning of Year		85,418	81,788
Common Stock Issued or Granted Under Stock Plans		3,289	3,630
Balance at End of Year		88,707	85,418
Premium on Common Stock		499,460	438,384
Treasury Stock (at par)		(296)	(330)
Accumulated Other Comprehensive Loss	[1]	(24,499)	(30,258)
Retained Earnings		474,167	439,218
Total Equity		1,037,539	932,432
Long-Term Debt	[2]	1,006,394	859,491
Total Capitalization		2,043,933	1,791,923
Current Liabilities:
Notes Payable		431,700	245,700
Current Portion of Long-Term Debt	[2]	29,454	149,909
Accounts Payable		186,400	272,998
Customer Deposits and Credit Balances		20,146	17,958
Environmental Remediation Costs		50,559	30,430
Taxes Accrued		2,336	2,328
Derivatives - Energy Related Liabilities		90,708	109,744
Interest Accrued		7,316	7,088
Pension Benefits		2,261	1,550
Other Current Liabilities		11,596	12,480
Total Current Liabilities		832,476	850,185
Deferred Credits and Other Noncurrent Liabilities:
Deferred Income Taxes - Net		295,945	344,520
Investment Tax Credits		0	149
Pension and Other Postretirement Benefits		76,068	115,373
Environmental Remediation Costs		76,064	97,742
Asset Retirement Obligations		57,943	42,502
Derivatives - Energy Related Liabilities		21,697	19,926
Derivatives - Other		10,943	10,732
Regulatory Liabilities		42,841	41,899
Finance Obligation		0	19,659
Other		22,990	14,815
Total Deferred Credits and Other Noncurrent Liabilities		$ 604,491	$ 707,317
Commitments and Contingencies (Note 15)
Total Capitalization and Liabilities		$ 3,480,900	$ 3,349,425

[1] Determined using a combined average statutory tax rate of 40%.

[2] Long-term debt maturities and sinking funds requirements for the succeeding five years are as follows (in thousands): 2016, $29,454; 2017, $172,558; 2018,$40,667; 2019,$260,783; and 2020, $74,476.