Liabilities Carried at Fair Value Measured on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair value, liabilities measured on recurring basis, derivative financial instruments, liabilities	$ 2,785	$ 4,070
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair value, liabilities measured on recurring basis, derivative financial instruments, liabilities
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair value, liabilities measured on recurring basis, derivative financial instruments, liabilities	2,785	4,070
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair value, liabilities measured on recurring basis, derivative financial instruments, liabilities
Interest Rate Swap Agreements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair value, liabilities measured on recurring basis, derivative financial instruments, liabilities	2,785	4,070
Interest Rate Swap Agreements | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair value, liabilities measured on recurring basis, derivative financial instruments, liabilities
Interest Rate Swap Agreements | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair value, liabilities measured on recurring basis, derivative financial instruments, liabilities	2,785	4,070
Interest Rate Swap Agreements | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair value, liabilities measured on recurring basis, derivative financial instruments, liabilities