Financial Instruments - Summary of Outstanding Interest Rate Swap (Parenthetical) (Detail) - Interest Rate Swap [Member] - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Interest rate swap, description of interest received	Interest that varied with the three-month LIBOR
Interest rate swap, fixed interest rate	1.41%	1.41%
June 2015 [Member]
Derivatives, Fair Value [Line Items]
Notional value	$ 25,000,000	$ 25,000,000
Interest rate swap, expiration date	2015-06	2015-06