CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment:
Utility Plant, at original cost	$ 2,261,409	$ 2,211,239
Accumulated Depreciation	(450,001)	(440,473)
Nonutility Property and Equipment, at cost	784,495	785,646
Accumulated Depreciation	(117,737)	(108,307)
Property, Plant and Equipment - Net	2,478,166	2,448,105
Investments:
Available-for-Sale Securities	14,960	14,810
Restricted	37,893	48,758
Investment in Affiliates	20,254	16,983
Total Investments	73,107	80,551
Current Assets:
Cash and Cash Equivalents	4,250	3,877
Accounts Receivable	179,662	178,359
Unbilled Revenues	47,502	40,044
Provision for Uncollectibles	(10,024)	(10,252)
Notes Receivable	11,819	11,800
Notes Receivable - Affiliate	1,508	3,134
Natural Gas in Storage, average cost	38,571	54,211
Materials and Supplies, average cost	6,762	5,088
Prepaid Taxes	11,382	21,753
Derivatives - Energy Related Assets	57,815	83,093
Other Prepayments and Current Assets	46,863	40,167
Total Current Assets	396,110	431,274
Regulatory and Other Noncurrent Assets:
Regulatory Assets	356,962	323,434
Derivatives - Energy Related Assets	19,489	16,238
Notes Receivable - Affiliate	13,275	13,275
Contract Receivables	29,039	28,609
Notes Receivable	31,888	35,439
Goodwill	8,139	8,880
Identifiable Intangible Assets	21,850	21,553
Other	65,959	64,575
Total Regulatory and Other Noncurrent Assets	546,601	512,003
Total Assets	3,493,984	3,471,933
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	55,373	42,841
Equity:
Common Stock	89,048	88,707
Premium on Common Stock	505,601	499,460
Treasury Stock (at par)	(262)	(296)
Accumulated Other Comprehensive Loss	(24,399)	(24,499)
Retained Earnings	523,454	474,167
Total Equity	1,093,442	1,037,539
Long-Term Debt	1,046,968	997,427
Total Capitalization	2,140,410	2,034,966
Current Liabilities:
Notes Payable	339,500	431,700
Current Portion of Long-Term Debt	28,604	29,454
Accounts Payable	151,006	186,400
Customer Deposits and Credit Balances	19,340	20,146
Environmental Remediation Costs	55,065	50,559
Taxes Accrued	3,737	2,336
Derivatives - Energy Related Liabilities	66,370	90,708
Dividends Payable	18,790	0
Interest Accrued	6,108	7,316
Pension Benefits	2,261	2,261
Other Current Liabilities	7,222	11,596
Total Current Liabilities	698,003	832,476
Deferred Credits and Other Noncurrent Liabilities:
Deferred Income Taxes - Net	333,572	295,945
Pension and Other Postretirement Benefits	77,720	76,068
Environmental Remediation Costs	85,263	76,064
Asset Retirement Obligations	58,054	57,943
Derivatives - Energy Related Liabilities	10,148	21,697
Derivatives - Other	13,118	10,943
Regulatory Liabilities	55,373	42,841
Other	22,323	22,990
Total Deferred Credits and Other Noncurrent Liabilities	$ 655,571	$ 604,491
Commitments and Contingencies
Total Capitalization and Liabilities	$ 3,493,984	$ 3,471,933
Excess Plant Removal Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	32,294	32,644
Deferred Revenues - Net
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	11,241	0
Societal Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	9,454	10,197
Energy Efficiency Tracker
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 2,384	$ 0