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Taxation - Income Tax Rate Reconciliation (Detail)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Income Tax Rate Reconciliation [Abstract]      
Provision at the U.S. federal statutory rate 34.00% 34.00% 34.00%
State taxes, net of federal benefit 1.90% 4.20% 3.20%
Foreign tax rate differential (2.50%) 0.00% (1.20%)
Valuation allowance 2.90% 10.50% 2.70%
Research credits (4.20%) (10.00%) (6.50%)
Stock-based compensation (0.40%) 0.30% 0.00%
Other 3.40% 6.30% 1.40%
Income tax expense effective rate 35.10% 45.30% 33.60%