Income Taxes - Difference Between the Company's Reported Provision for Income Taxes and the U.S. Federal Statutory Rate (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
U.S. federal tax at statutory rate	35.00%	35.00%	35.00%
State and local taxes - net of federal benefit	4.20%	4.10%	2.40%
Credits and deductions related to research activities	(1.70%)	(3.00%)
Release of previously unrecognized tax benefits			(7.50%)
Other, net	(0.60%)		1.00%
Provision for income taxes	36.90%	36.10%	30.90%