Financial Instruments (Bonds) - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Investments Debt And Equity Securities [Abstract]
Corporate and municipal bonds	$ 41.4	$ 40.8
Maturity dates of bonds, start date	2016-10
Maturity dates of bonds, end date	2021-10