Leases - Components of Lease Costs (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Finance lease cost - interest on lease liabilities		$ 3,256	$ 4,265
Operating lease cost, excluding short-term leases	[1]	716	866
Short-term lease cost	[2]	5,760	3,535
Variable lease cost	[3]	322	3
Total lease cost		$ 10,054	$ 8,669

[1] Operating lease cost reflect a single lease cost, calculated so that the cost of the lease is allocated over the lease term on a straight-line basis.

[2] Short-term lease costs are reported at gross amounts and primarily represent costs incurred for drilling rigs, most of which are short-term contracts not recognized as a right-of-use asset and lease liability on the Condensed Consolidated Balance Sheets.

[3] Variable lease costs primarily represent differences between minimum payment obligations and actual operating charges incurred by the Company related to its long-term leases.