Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	$ 76,942	$ 80,324	$ 137,766	$ 134,456
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	134,422	125,077	262,372	244,391
Deferred income taxes	3,896	24,493	43,712	47,351
Changes in current assets and liabilities:
Accounts receivable, net of allowances	6,018	35,997	(33,662)	(23,208)
Accrued utility revenue	42,100	41,100	(200)	(1,200)
Deferred purchased gas costs	111,021	(62,224)	103,906	(108,991)
Accounts payable	(38,471)	(91,674)	11,704	(10,082)
Accrued taxes	7,614	(4,801)	(1,158)	(1,424)
Other current assets and liabilities	5,163	46,238	(17,696)	27,234
Gains on sale	(2,563)	(4,137)	(4,597)	(5,964)
Changes in undistributed stock compensation	1,512	3,766	5,719	6,869
AFUDC	(1,133)	(1,024)	(2,104)	(2,296)
Changes in other assets and deferred charges	(15,239)	(15,150)	(21,821)	(20,476)
Changes in other liabilities and deferred credits	2,954	19,462	(729)	41,775
Net cash provided by operating activities	334,236	197,447	483,212	328,435
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions	(203,640)	(175,444)	(425,094)	(387,843)
Acquisition of businesses, net of cash acquired	(9,261)	0	(199,758)	0
Restricted cash	785	(16,649)	18,667	(16,649)
Changes in customer advances	9,689	8,947	21,105	13,593
Miscellaneous inflows	4,892	7,060	9,443	10,620
Miscellaneous outflows	0	0	(1,400)	0
Net cash used in investing activities	(197,535)	(176,086)	(577,037)	(380,279)
CASH FLOW FROM FINANCING ACTIVITIES:
Issuance of common stock, net	20,713	237	20,881	515
Dividends paid	(36,001)	(32,316)	(69,960)	(62,904)
Issuance of long-term debt, net	93,165	17,719	344,674	287,336
Retirement of long-term debt	(78,409)	(10,716)	(206,848)	(46,460)
Change in credit facility and commercial paper	(120,000)	(10,000)	30,000	(119,000)
Change in short-term debt	(5,000)	0	0	0
Principal payments on capital lease obligations	(722)	0	(1,156)	0
Other	(534)	(472)	(1,319)	1,527
Net cash provided by (used in) financing activities	(126,788)	(35,548)	116,272	61,014
Effects of currency translation on cash and cash equivalents	(570)	0	(428)	0
Change in cash and cash equivalents	9,343	(14,187)	22,019	9,170
Cash and cash equivalents at beginning of period	39,566	41,077	26,890	17,720
Cash and cash equivalents at end of period	48,909	26,890	48,909	26,890
Supplemental information:
Interest paid, net of amounts capitalized	34,213	31,787	67,978	61,401
Income taxes paid	$ 28,479	$ 12,246	$ 40,480	$ 15,565