Agreed-Upon Values Associated With the Properties and the Separate Interests, Along with a Discussion of the Interests (Parenthetical) (Detail) (USD $)	9 Months Ended		12 Months Ended			12 Months Ended											9 Months Ended		12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2012 Sixty One	Aug. 23, 2012 Separate Interests	Sep. 30, 2011 Separate Interests	Dec. 31, 2012 Nymex Thresholds Price Per Barrel Oil Of Ninety Sixty One	Dec. 31, 2012 Nymex Thresholds Price Per Barrel Oil Of Hundred Sixty One	Dec. 31, 2012 Nymex Thresholds Price Per Barrel Oil Of One Hundred And Ten Sixty One	Dec. 31, 2012 Nymex Thresholds Price Per Barrel Oil Of One Hundred And Twenty Five Sixty One	Dec. 31, 2012 Nymex Thresholds Price Per Barrel Oil Of One Hundred And Fifty Sixty One	Dec. 31, 2012 Nymex Thresholds Price Per Mmbtu Of Five Sixty One	Dec. 31, 2012 Nymex Thresholds Price Per Mmbtu Of Six Sixty One	Dec. 31, 2012 Nymex Thresholds Price Per Mmbtu Of Seven Point Five Sixty One	Dec. 31, 2012 Nymex Thresholds Price Per Mmbtu Of Ten Sixty One	Dec. 31, 2012 Nymex Thresholds Price Per Mmbtu Of Twelve Sixty One	Dec. 31, 2012 Colorado And Kansas	Sep. 30, 2012 Wyoming And Montana	Sep. 30, 2012 Maximum	Dec. 31, 2012 Maximum	Sep. 30, 2012 Minimum	Dec. 31, 2012 Minimum
Related Party Transaction [Line Items]
Additional consideration payable to sellers			Ten years after the closing date
Nymex thresholds per barrel of oil						90	100	110	125	150
Number of consecutive days for incremental purchase consideration			61 days
Incremental purchase considerations payable to sellers						$ 250,000	$ 250,000	$ 500,000	$ 500,000	$ 2,000,000
Nymex thresholds per MMbtu											5.00	6.00	7.50	10.00	12.00
Additional considerations for sellers on Oil reserves																250,000
Number of units required for additional consideration																20,000
Additional considerations for sellers on natural gas																150,000
Number of units required for additional consideration																150,000
Reserve factor multiplier effect																			5		1
Maximum increase in purchase price																5,000,000	25,000,000
Sellers retained interest		70.00%
Percentage of recovery received		125.00%
Increase in oil price per barrel																		100		90
Maximum future consideration																		19,800,000		5,200,000
Accrual amount due to increase in oil price	500,000
funds paid contemporaneously with the execution of PSA				5,101,047
Recognized gain					$ 2,479,934