Derivative Financial Instruments (Derivative Instruments, Gain (Loss) (Detail) - Jun. 30, 2015 - Swap [Member]	$ / Unit
Product [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	Apr. 01, 2015
Derivative, Maturity Date	Apr. 30, 2015
Underlying, Derivative Volume	2,500
Derivative, Swap Type, Fixed Price	13.000
Product One [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	May 01, 2015
Derivative, Maturity Date	May 31, 2015
Underlying, Derivative Volume	1,390
Derivative, Swap Type, Fixed Price	13.000
Product Two [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	Jun. 01, 2015
Derivative, Maturity Date	Jun. 30, 2015
Underlying, Derivative Volume	950
Derivative, Swap Type, Fixed Price	13.000
Product Three [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	Jul. 01, 2015
Derivative, Maturity Date	Jul. 31, 2015
Underlying, Derivative Volume	890
Derivative, Swap Type, Fixed Price	13.000
Product Four [Member]
Derivative [Line Items]
Derivative, Type of Instrument	Swap
Derivative, Inception Date	Apr. 01, 2015
Derivative, Maturity Date	Mar. 31, 2016
Underlying, Derivative Volume	500
Derivative, Swap Type, Fixed Price	2.420