Financial Instruments - (Bonds) Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Corporate and municipal bonds	$ 37.0	$ 36.4
Maturity dates of bonds, start date	2015-07
Maturity dates of bonds, end date	2019-11
Interest Rate Swap [Member] | June 2015 [Member]
Schedule of Available-for-sale Securities [Line Items]
Interest rate swap, expiration date	2015-06	2015-06