Reconciliation of Statutory Federal Income Tax Rate to Company Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	35.00%	35.00%	35.00%
State and local taxes	(2.20%)	(1.60%)	(0.30%)
Orphan Drug & General Business Credit	34.80%	29.30%	14.70%
Stock compensation expense	(2.80%)	(2.40%)	(1.70%)
Changes in the fair value of contingent acquisition consideration payable	0.20%	(3.60%)	(2.90%)
Subpart F income	(8.40%)	(9.20%)
Foreign tax rate differential	(46.20%)	(51.50%)	(45.40%)
Other	(2.90%)	(3.60%)	1.60%
Valuation allowance/Deferred benefit	(18.50%)	0.30%	(0.90%)
Effective income tax rate	(11.00%)	(7.30%)	0.10%