Fair Value Of Assets And Liabilities (Fair Value And Carrying Value Of Preferred Stocks And Long-Term Debt) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stocks with mandatory redemption requirements	$ 20,971	$ 22,036
Long-term debt (excluding capital lease obligations)	5,216,771	5,366,642
Preferred stocks with mandatory redemption requirements	27,649	26,458
Long-term debt (excluding capital lease obligations)	6,692,534	6,230,547
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stocks with mandatory redemption requirements	0
Long-term debt (excluding capital lease obligations)	2,410,390
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stocks with mandatory redemption requirements	0
Long-term debt (excluding capital lease obligations)	1,665,503
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stocks with mandatory redemption requirements	27,649
Long-term debt (excluding capital lease obligations)	$ 2,616,641