Derivative Instruments - Financial Information Related to Cash Flow Hedges of Future Revenues (Detail)	12 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2012 Cash Flow Hedging [Member] USD ($)	Dec. 31, 2011 Cash Flow Hedging [Member] USD ($)	Dec. 31, 2010 Cash Flow Hedging [Member] USD ($)	Dec. 31, 2012 Cash Flow Hedging [Member] EUR (€)	Dec. 31, 2011 Cash Flow Hedging [Member] EUR (€)
Derivative [Line Items]
Notional balance of outstanding contracts versus the dollar							€ 88,680,000	€ 85,105,000
Hedge effectiveness							100.00%	100.00%
Net gains and (losses) included in revenue	$ 7,203,000	$ (5,109,000)	$ 3,689,000	$ 4,201,000	$ (4,159,000)	$ (630,000)