Costs of Oil and Gas Properties (Tables)

12 Months Ended

Dec. 31, 2012

Oil and Gas Property, Successful Effort Method, Gross [Abstract]

Costs incurred in connection with the company's oil and gas producing activities

The following table sets forth certain information with respect to costs incurred in connection with the Company’s oil and gas producing activities during the years ended December 31, 2012, 2011 and 2010.

	2012		2011		2010
	(In thousands)
Property acquisitions:
Proved	$	41,098	$	—	$	9,556
Unproved	72,235		61,236		29,680
Developmental costs	349,972		328,418		238,197
Exploratory costs	10,898		27,425		7,528
Total	$	474,203	$	417,079	$	284,961

Schedule of net capitalized costs for oil and gas properties

The following table sets forth the capitalized costs for oil and gas properties as of December 31, 2012 and 2011.

	2012			2011
	(In thousands)
Proved properties	$	2,482,185		$	2,021,181
Unproved properties	88,618			81,904
Total capitalized costs	2,570,803			2,103,085
Accumulated depletion	(1,234,626		)	(1,095,197		)
Net capitalized costs	$	1,336,177		$	1,007,888