Assets Measured at Fair Value Subject to Three-Tier Hierarchy (Detail) (Financial assets measured on a recurring basis, USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Fair Value Measurements at Reporting Date Using Quoted prices in active markets for identical assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	$ 29,378	$ 11,365
Fair Value Measurements at Reporting Date Using Quoted prices in active markets for identical assets (Level 1) | Cash and cash equivalents - cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents - cash equivalents	14,520	10
Fair Value Measurements at Reporting Date Using Quoted prices in active markets for identical assets (Level 1) | Mutual funds - fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	13,724	10,479
Fair Value Measurements at Reporting Date Using Quoted prices in active markets for identical assets (Level 1) | Mutual funds - equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	1,134	876
Fair Value Measurements at Reporting Date Using Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	61,995	87,825
Fair Value Measurements at Reporting Date Using Significant other observable inputs (Level 2) | Cash and cash equivalents - cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents - cash equivalents	60,508	84,726
Fair Value Measurements at Reporting Date Using Significant other observable inputs (Level 2) | Interest rate swap derivative
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swap derivative	$ 1,487	$ 3,099