Financial Instruments (Bonds) - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Corporate and municipal bonds	$ 41.2	$ 40.8
Maturity dates of bonds, start date	2016-04
Maturity dates of bonds, end date	2021-10