Capitalized Costs and Accumulated Depreciation, Depletion and Amortization (Tables)

9 Months Ended

Sep. 30, 2017

Extractive Industries [Abstract]

Capitalized Costs and Accumulated Depreciation, Depletion and Amortization

	September 30, 2017			December 31, 2016
	(in thousands)
Natural gas and oil properties:
Properties subject to depletion	$	10,172,411		$	9,462,350
Unproved properties		2,888,979			2,923,803
Total		13,061,390			12,386,153
Accumulated depreciation, depletion and amortization		(3,492,614	)		(3,129,816	)
Net capitalized costs	$	9,568,776		$	9,256,337

^(a) Includes capitalized asset retirement costs and the associated accumulated amortization.