Fair Value Measurements - Additional Information (Detail) (USD $)			9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Treasury lock hedge	Sep. 30, 2012 Maximum	Sep. 30, 2012 Level 3 Inputs	Dec. 31, 2011 Level 3 Inputs	Sep. 30, 2012 Level 2 Inputs	Dec. 31, 2011 Level 2 Inputs
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of hedge	$ 483,000		$ 483,000		$ 0		$ 483,000
Hedge maturity date			2012-10
Contingent consideration	22,861,000	9,921,000			22,861,000	9,921,000	0	0
Contingent consideration, Current					14,000,000
Contingent liability				24,900,000
Debt obligation, fair value							1,340,000,000	1,410,000,000
Long-term debt	$ 1,297,150,000	$ 1,384,639,000