Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2016		Dec. 31, 2015
Assets:
Commodity derivative assets – current	$ 0		$ 97,956
Liabilities:
Commodity derivative liabilities – current	(4,527)
Derivative Liability, Noncurrent	(13,715)		0
Fair Value, Measurements, Recurring
Assets:
Assets of SERP 1	4,220	[1]	4,123
Liabilities:
Deferred compensation – SERP obligations 1	0		(4,125)
Fair Value, Measurements, Recurring | Level 1
Assets:
Assets of SERP 1	4,220	[1]	4,123
Liabilities:
Deferred compensation – SERP obligations 1	0		(4,125)
Fair Value, Measurements, Recurring | Level 2
Assets:
Assets of SERP 1	0		0
Liabilities:
Deferred compensation – SERP obligations 1	0		0
Fair Value, Measurements, Recurring | Level 3
Assets:
Assets of SERP 1	0		0
Liabilities:
Deferred compensation – SERP obligations 1	0		0
Fair Value, Measurements, Recurring | Commodity contracts
Assets:
Commodity derivative assets – current			97,956
Liabilities:
Commodity derivative liabilities – current	(4,527)
Derivative Liability, Noncurrent	(13,715)
Fair Value, Measurements, Recurring | Commodity contracts | Level 1
Assets:
Commodity derivative assets – current			0
Liabilities:
Commodity derivative liabilities – current	0
Derivative Liability, Noncurrent	0
Fair Value, Measurements, Recurring | Commodity contracts | Level 2
Assets:
Commodity derivative assets – current			97,956
Liabilities:
Commodity derivative liabilities – current	(4,527)
Derivative Liability, Noncurrent	(13,715)
Fair Value, Measurements, Recurring | Commodity contracts | Level 3
Assets:
Commodity derivative assets – current			$ 0
Liabilities:
Commodity derivative liabilities – current	0
Derivative Liability, Noncurrent	$ 0

[1] The amounts associated with these liabilities were included in “Liabilities subject to compromise” as of June 30, 2016 (see Note 3).