Borrowings (Total Obligations Under Senior Secured Notes) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Senior Secured Notes	$ 57,194	$ 85,762
Secured Debt [Member]
Debt Instrument [Line Items]
Senior Secured Notes	917,848	932,089
Senior Notes Due March 18, 2013 (New Debt) [Member]
Debt Instrument [Line Items]
Unamortized debt discount	(18,900)	(16,500)
Senior Notes Due March 18, 2013 (New Debt) [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Senior Secured Notes	70,000	0
Senior Secured Notes	70,000	0
Senior Secured Notes Due 2016 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Senior Secured Notes	920,767	935,296
Unamortized debt discount	$ (2,919)	$ (3,207)

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Carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

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Carrying value as of the balance sheet date of the portion of long-term notes having the highest claim on the assets of the issuer in case of bankruptcy or liquidation, due within one year or the normal operating cycle, if longer. Senior note holders are paid off in full before any payments are made to debt holders having a lesser priority of repayment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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