Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities
Net income	$ 34,152	$ 38,789
Adjustments to reconcile net income to net cash provided by (used in) operating activities
Depreciation of property, plant and equipment	39,726	37,911
Other amortization	935	1,419
Provision for loan losses	1,858	3,546
Loans receivable originated and purchased, held for sale	(79,224)	(89,087)
Proceeds from sale of loans receivable, held for sale	102,254	85,252
Change in deferred income taxes	19,967	21,260
Change in excess tax benefits from share-based payment arrangements	(414)	(44)
Allowance for equity funds used during construction	(1,215)	(1,940)
Changes in assets and liabilities
Decrease in accounts receivable and unbilled revenues, net	14,335	37,562
Increase in fuel oil stock	(29,272)	(14,458)
Increase in regulatory assets	(17,746)	(13,948)
Increase (decrease) in accounts, interest and dividends payable	38,148	(36,991)
Change in prepaid and accrued income taxes and utility revenue taxes	(50,933)	(41,126)
Contributions to defined benefit pension and other postretirement benefit plans	(21,476)	(26,815)
Change in other assets and liabilities	(2,776)	(17,046)
Net cash provided by (used in) operating activities	48,319	(15,716)
Cash flows from investing activities
Available-for-sale investment and mortgage-related securities purchased	(26,705)	(53,931)
Principal repayments on available-for-sale investment and mortgage-related securities	36,504	46,355
Net increase in loans held for investment	(66,934)	(34,212)
Proceeds from sale of real estate acquired in settlement of loans	3,046	3,371
Capital expenditures	(71,041)	(65,300)
Contributions in aid of construction	11,710	22,855
Other	869
Net cash used in investing activities	(112,551)	(80,862)
Cash flows from financing activities
Net increase in deposit liabilities	82,704	55,172
Net increase in short-term borrowings with original maturities of three months or less	50,244	87,467
Net decrease in retail repurchase agreements	(2,680)	(379)
Proceeds from issuance of long-term debt	50,000
Repayment of long-term debt	(50,000)	(57,500)
Change in excess tax benefits from share-based payment arrangements	414	44
Net proceeds from issuance of common stock	4,703	5,940
Common stock dividends	(24,394)	(23,855)
Preferred stock dividends of subsidiaries	(473)	(473)
Other	(3,240)	(3,757)
Net cash provided by financing activities	107,278	62,659
Net increase (decrease) in cash and cash equivalents	43,046	(33,919)
Cash and cash equivalents, beginning of period	219,662	270,265
Cash and cash equivalents, end of period	$ 262,708	$ 236,346