Accumulated Other Comprehensive Income (Loss) - Schedule of Changes in Accumulated Other Comprehensive Income Loss (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, net of tax	$ 17,952	$ 83,300
Other comprehensive income (loss) before reclassifications:
Change in fair value of derivatives	4,600	22,900
Foreign currency translations		(3,600)
Income tax effect	(1,600)	(8,200)
Net of tax	3,000	11,100
Amounts reclassified from accumulated other comprehensive income:
Operating revenue: oil/natural gas production	12,800	36,800
Other operational expenses	(6,000)
Income tax effect	(4,500)	(13,200)
Net of tax	2,300	23,600
Other comprehensive income (loss), net of tax	700	(12,500)
Ending balance, net of tax	18,741	70,800
Cash Flow Hedges
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, net of tax	24,000	86,800
Other comprehensive income (loss) before reclassifications:
Change in fair value of derivatives	4,600	22,900
Foreign currency translations		0
Income tax effect	(1,600)	(8,200)
Net of tax	3,000	14,700
Amounts reclassified from accumulated other comprehensive income:
Income tax effect	(4,500)	(13,200)
Net of tax	8,300	23,600
Other comprehensive income (loss), net of tax	(5,300)	(8,900)
Ending balance, net of tax	18,700	77,900
Foreign Currency Items
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, net of tax	(6,000)	(3,500)
Other comprehensive income (loss) before reclassifications:
Change in fair value of derivatives	0	0
Foreign currency translations		(3,600)
Income tax effect	0	0
Net of tax	0	(3,600)
Amounts reclassified from accumulated other comprehensive income:
Operating revenue: oil/natural gas production	0	0
Other operational expenses	(6,000)
Income tax effect	0	0
Net of tax	(6,000)	0
Other comprehensive income (loss), net of tax	6,000	(3,600)
Ending balance, net of tax	$ 0	$ (7,100)