Fair Value of Debt (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Fair Value Measurements [Line Items]
Fair value of debt	$ 1,192,666
Quoted Prices In Active Markets (Level 1)
Fair Value Measurements [Line Items]
Fair value of debt	824,748
Significant Other Observable Inputs (Level 2)
Fair Value Measurements [Line Items]
Fair value of debt	$ 367,918

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

No definition available.

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant