Schedule Of Long-Term Obligations (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Debt Obligations [Line Items]
Single draw Eurodollar five-year term loan bearing interest equal to the British Bankers Association LIBOR Rate ("BBA LIBOR") plus an applicable margin based on the Company's consolidated leverage ratio (consolidated funded indebtedness to consolidated EBITDA)	$ 250,000	$ 0
Eurodollar loans under five-year revolving credit agreement bearing annual interest equal to the British Bankers Association LIBOR Rate ("BBA LIBOR") plus an applicable margin based on the Company's consolidated leverage ratio (consolidated funded indebtedness to consolidated EBITDA)	0	100,000
Other long-term obligations	1,405	1,710
Contingent consideration	16,935	21,595
Unsecured acquisition obligations, net of imputed interest, payable in various installments through 2015	15,434	20,996
Total long-term obligations	803,833	653,910
Less: current installments	307,128	397,132
Long-term obligations, excluding current installments	496,705	256,778
Option 2012 [Member]
Debt Obligations [Line Items]
Principal amount of convertible debentures	275,000	275,000
Unamortized discount	(3,685)	(9,059)
Option 2014 [Member]
Debt Obligations [Line Items]
Principal amount of convertible debentures	275,000	275,000
Unamortized discount	$ (26,256)	$ (31,332)