Fair Value Hierarchy of Financial Assets Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents (money market accounts and commercial paper investments)	23,598		111,775
Hedges of interest rate risk	(90)	[1]	(36)	[1]
Acquisition contingent consideration obligations			(1,197)
Fair Value Assets And Liabilities Measured On Recurring Basis Net, Total	23,508		110,542
Cash equivalents (money accounts market and commercial paper investments)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Technique (Approach)	Market		Market
Hedges of interest rate risk
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Technique (Approach)	Market	[1]	Market	[1]
Acquisition contingent consideration obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Technique (Approach)			Income
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents (money market accounts and commercial paper investments)	23,598		111,775
Fair Value Assets And Liabilities Measured On Recurring Basis Net, Total	23,598		111,775
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Hedges of interest rate risk	(90)	[1]	(36)	[1]
Fair Value Assets And Liabilities Measured On Recurring Basis Net, Total	(90)		(36)
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition contingent consideration obligations			(1,197)
Fair Value Assets And Liabilities Measured On Recurring Basis Net, Total			(1,197)

[1] ICG's respective counterparties under the arrangements provide quarterly statements of market values of those instruments based on significant inputs that are observable or can be derived principally from, or corroborated by, observable market data for substantially the full term of the asset or liability.