Accumulated Other Comprehensive Income (Loss) - Schedule of Changes in Accumulated Other Comprehensive Income Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, net of tax	$ 18,700	$ 70,800	$ 17,952	$ 83,300
Other comprehensive income (loss) before reclassifications:
Change in fair value of derivatives	(8,600)	(18,800)	(4,000)	4,100
Foreign currency translations		1,300		(2,300)
Income tax effect	3,100	6,900	1,400	(1,300)
Net of tax	(5,500)	(10,600)	(2,600)	500
Amounts reclassified from accumulated other comprehensive income:
Operating revenue: oil/natural gas production	8,900	30,400	21,700	67,200
Other operational expenses			(6,000)
Income tax effect	(3,100)	(10,900)	(7,700)	(24,100)
Net of tax	5,800	19,500	8,000	43,100
Other comprehensive income (loss), net of tax	(11,300)	(30,100)	(10,600)	(42,600)
Ending balance, net of tax	7,385	40,700	7,385	40,700
Cash Flow Hedges
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, net of tax	18,700	77,900	24,000	86,800
Other comprehensive income (loss) before reclassifications:
Change in fair value of derivatives	(8,600)	(18,800)	(4,000)	4,100
Foreign currency translations		0		0
Income tax effect	3,100	6,900	1,400	(1,300)
Net of tax	(5,500)	(11,900)	(2,600)	2,800
Amounts reclassified from accumulated other comprehensive income:
Other operational expenses			0
Income tax effect	(3,100)	(10,900)	(7,700)	(24,100)
Net of tax	5,800	19,500	14,000	43,100
Other comprehensive income (loss), net of tax	(11,300)	(31,400)	(16,600)	(40,300)
Ending balance, net of tax	7,400	46,500	7,400	46,500
Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive income:
Operating revenue: oil/natural gas production	8,900		21,700
Foreign Currency Items
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, net of tax	0	(7,100)	(6,000)	(3,500)
Other comprehensive income (loss) before reclassifications:
Change in fair value of derivatives	0	0	0	0
Foreign currency translations		1,300		(2,300)
Income tax effect	0	0	0	0
Net of tax	0	1,300	0	(2,300)
Amounts reclassified from accumulated other comprehensive income:
Operating revenue: oil/natural gas production	0	0	0	0
Other operational expenses			(6,000)
Income tax effect	0	0	0	0
Net of tax	0	0	(6,000)	0
Other comprehensive income (loss), net of tax	0	1,300	6,000	(2,300)
Ending balance, net of tax	$ 0	$ (5,800)	$ 0	$ (5,800)