Summary of Significant Accounting Policies and Procedures - Assets and Liabilities Carried at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Short-term investments:
Short-term investments	$ 11,311	$ 138,311
Liabilities:
Contingent consideration	123,008	117,197
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Liabilities:
Derivative Liability, Fair Value, Gross Liability	11,544
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Liabilities:
Contingent consideration	123,008	117,197
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | Level 1 [Member]
Cash equivalents:
Cash equivalents	69,080	54,229
Corporate Debt Securities [Member]
Short-term investments:
Short-term investments	9,300	126,200
Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Cash equivalents:
Cash equivalents		7,599
Short-term investments:
Short-term investments	9,311	126,159
Asset- backed Securities [Member]
Short-term investments:
Short-term investments	2,000	12,100
Asset- backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Short-term investments:
Short-term investments	$ 2,000	$ 12,152