Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities
Net income	$ 140,120	$ 115,425	$ 84,901
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment	148,152	154,523	151,282
Other amortization	19,318	4,605	5,389
Provision for loan losses	15,009	20,894	32,000
Impairment of utility plant	9,215
Loans receivable originated and purchased, held for sale	(267,656)	(360,527)	(443,843)
Proceeds from sale of loans receivable, held for sale	273,932	392,406	471,194
Net losses on sale of investment and mortgage-related securities			32,034
Other-than-temporary impairment on available-for-sale mortgage-related securities			15,444
Changes in deferred income taxes	79,444	97,791	12,787
Changes in excess tax benefits from share-based payment arrangements	35	45	310
Allowance for equity funds used during construction	(5,964)	(6,016)	(12,222)
Change in cash overdraft	(2,688)	(141)
Changes in assets and liabilities
Decrease (increase) in accounts receivable and unbilled revenues, net	(77,326)	(25,880)	59,550
Increase in fuel oil stock	(18,843)	(74,044)	(946)
Increase (decrease) in accounts, interest and dividends payable	(34,480)	22,410	(12,472)
Changes in prepaid and accrued income taxes and utility revenue taxes	73,153	(5,252)	(61,977)
Contributions to defined benefit pension and other postretirement benefit plans	(74,961)	(31,792)	(25,354)
Changes in other assets and liabilities	(26,094)	36,270	(39,491)
Net cash provided by operating activities	250,366	340,717	268,586
Cash flows from investing activities
Available-for-sale investment and mortgage-related securities purchased	(361,876)	(714,552)	(297,864)
Principal repayments on available-for-sale investment and mortgage-related securities	389,906	465,437	357,233
Proceeds from sale of available-for-sale investment and mortgage-related securities	32,799		185,134
Net decrease (increase) in loans held for investment	(181,080)	118,892	484,960
Proceeds from sale of real estate acquired in settlement of loans	8,020	5,967	1,555
Capital expenditures	(235,116)	(182,125)	(288,879)
Contributions in aid of construction	23,534	22,555	14,170
Other	(2,974)	5,092	1,199
Net cash provided by (used in) investing activities	(326,787)	(278,734)	457,508
Cash flows from financing activities
Net increase (decrease) in deposit liabilities	94,660	(83,388)	(121,415)
Net increase (decrease) in short-term borrowings with original maturities of three months or less	43,898	(17,066)	41,989
Net increase (decrease) in retail repurchase agreements	10,910	(60,308)	(3,829)
Proceeds from other bank borrowings			310,000
Repayments of other bank borrowings	(15,000)		(689,517)
Proceeds from issuance of long-term debt	125,000		153,186
Repayment of long-term debt	(150,000)
Changes in excess tax benefits from share-based payment arrangements	(35)	(45)	(310)
Net proceeds from issuance of common stock	15,979	22,706	15,329
Common stock dividends	(106,812)	(93,034)	(96,843)
Preferred stock dividends of subsidiaries	(1,890)	(1,890)	(1,890)
Change in cash overdraft			(9,545)
Other	(675)	(2,229)	(2,762)
Net cash provided by (used in) financing activities	16,035	(235,254)	(405,607)
Net increase (decrease) in cash and cash equivalents	(60,386)	(173,271)	320,487
Cash and cash equivalents, January 1	330,651	503,922	183,435
Cash and cash equivalents, December 31	$ 270,265	$ 330,651	$ 503,922