Exit Activities (Detail) $ in Thousands	1 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016 USD ($)	Feb. 29, 2016 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Restructuring and Related Activities [Abstract]
Severance and Termination Benefits	$ 300	$ 800
Restructuring and Related Cost, Number of Positions Eliminated	18	10
Firm Transportation Obligation [Roll Forward]
Balance at beginning of period			$ 13,461	$ 14,790	$ 14,790
Accretion			317	445	942
Cash payments, net			(1,059)	$ (2,271)
Balance at end of period	$ 12,719		12,719		$ 13,461
Severance and Termination Benefits Paid	700
Liabilities Subject to Compromise, Severance and Termination Benefits	400		$ 400
Restructuring and Related Cost, Expected Number of Positions Eliminated			26
Severance, Termination and Retention Benefits Expected			$ 1,700
Severance and Termination Benefits Expected			1,200
Retention Bonuses Expected			500
Liabilities Subject to Compromise, Early Contract Termination Fees	$ 1,300		$ 1,300