Supplemental Oil and Gas Reserve Information - Unaudited - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 MBoe $ / bbl $ / MMBTU	Dec. 31, 2015 location MBoe $ / bbl $ / MMBTU	Dec. 31, 2014 location MBoe $ / bbl $ / MMBTU
Oil and Gas Exploration and Production Industries Disclosures [Abstract]
Purchases of reserves in place (Energy)	66,936	2,565	1,799
Additions due to extensions and discoveries (Energy)	14,876	46,640	92,596
Estimated extensions and discoveries of reserves associated with new wells (Energy)	6,214	20,362	34,404
Percentage of reserves produced from wells in certain formations	100.00%	100.00%	100.00%
Additional proved undeveloped reserves (Energy)	6,493	26,278	58,192
Percentage of proved undeveloped reserves	100.00%	100.00%	100.00%
Divested reserves associated with non-operated properties (Energy)	7,635	0	8,448
Net positive (negative) revisions of previous estimates (Energy)	31,136	(84,635)	(25,117)
Percentage of net positive (negative) revisions	14.00%	(31.00%)	(11.00%)
Proved undeveloped locations | location		259	80
Proved undeveloped locations, net | location		190.8	56.2
Proved undeveloped reserves, decrease (Energy)		71,495	21,411
Discount rate of future cash flows	10.00%
Unweighted arithmetic average first-day-of-the-month prices for oil, price per Bbl | $ / bbl	42.60	50.16	95.28
Unweighted arithmetic average first-day-of-the-month prices for natural gas, price per MMBtu | $ / MMBTU	2.47	2.63	4.35