CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
OPERATING ACTIVITIES:
Net Income	$ 92,556	$ 77,376	$ 73,420
Items not affecting cash:
Depreciation	100,926	91,769	89,039
Amortization of debt issue costs, discount and deferred hedge gain	1,032	1,827	2,168
Amortization of nonvested shares	2,133	1,622	1,627
Equity portion of allowance for funds used during construction	(1,877)	(6,564)	(2,113)
Loss (gain) on disposition of assets	811	11	(287)
Deferred income taxes	64,065	48,783	47,014
Changes in current assets and liabilities:
Restricted cash	146	746	1,119
Accounts receivable	(3,847)	455	11,913
Inventories	(8,831)	(3,396)	23,436
Other current assets	(3,551)	8,155	(667)
Accounts payable	(1,928)	(12,766)	(9,224)
Accrued expenses	1,883	31,064	(48,396)
Regulatory assets	1,684	(13,575)	1,109
Regulatory liabilities	16,020	(12,449)	(19,601)
Other noncurrent assets	(30,048)	5,332	(3,928)
Other noncurrent liabilities	2,583	530	(49,825)
Cash provided by operating activities	233,757	218,920	116,804
INVESTING ACTIVITIES:
Property, plant, and equipment additions	(188,730)	(228,373)	(189,360)
Asset acquisition	0	(12,372)	0
Proceeds from sale of assets	209	69	326
Cash used in investing activities	(188,521)	(240,676)	(189,034)
FINANCING ACTIVITIES:
Dividends on common stock	(51,909)	(48,997)	(48,186)
Issuance of long-term debt	0	225,000	304,833
Repayment of long-term debt	(6,589)	(231,152)	(137,800)
Line of credit borrowings	80,000	695,000	348,000
Line of credit repayments	(233,000)	(608,000)	(390,000)
Issuances of short-term borrowings, net	166,934	0	0
Treasury stock activity	153	(185)	(741)
Financing costs	(1,131)	(8,020)	(10,824)
Cash (used in) provided by financing activities	(45,542)	23,646	65,282
(Decrease) Increase in Cash and Cash Equivalents	(306)	1,890	(6,948)
Cash and Cash Equivalents, beginning of period	6,234	4,344	11,292
Cash and Cash Equivalents, end of period	$ 5,928	$ 6,234	$ 4,344