Reconciliation of Statutory Federal Income Tax Rate to Company Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Federal statutory income tax rate	35.00%	35.00%	35.00%
State and local taxes	0.40%	(2.20%)	(1.60%)
Orphan Drug & General Business Credit	7.50%	34.80%	29.30%
Stock compensation expense	4.60%	(2.80%)	(2.40%)
Changes in the fair value of contingent acquisition consideration payable	0.90%	0.20%	(3.60%)
Subpart F income		(8.40%)	(9.20%)
Foreign tax rate differential	(18.60%)	(46.20%)	(51.50%)
Section 162(m) limitation	(5.40%)	(1.30%)	(1.70%)
Other	0.30%	(1.60%)	(1.90%)
Valuation allowance/deferred benefit	(0.50%)	(18.50%)	0.30%
Effective income tax rate	24.20%	(11.00%)	(7.30%)