Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Minimum commitments for unrecorded unconditional purchase obligations

At December 31, 2017, total minimum commitments from long-term non-cancelable operating leases, drilling rig commitments, seismic purchase obligations, fracturing services obligations, other purchase obligations and transportation and storage service commitments, based on current transportation and storage rates and the foreign currency exchange rates used to convert Canadian dollars and British pounds into United States dollars at December 31, 2017, were as follows (in thousands):

	Total Minimum Commitments
2018	$	1,855,005
2019	1,068,994
2020	800,078
2021	567,840
2022	478,480
2023 and beyond	944,911
	$	5,715,308