Leases (Tables)

12 Months Ended

Dec. 31, 2021

Leases [Abstract]

Schedule of lease costs

The following table provides information related to our lease costs (dollars in thousands):

	For the Year Ended December 31,
	2021		2020		2019
Operating Lease Cost - Purchased Power Lease Contracts	$	105,762	$	68,883	42,190
Operating Lease Cost - Land, Property, and Other Equipment	18,498		18,493		18,038
Total Operating Lease Cost	124,260		87,376		60,228
Variable lease cost (a)	118,969		122,331		114,015
Short-term lease cost	3,872		3,804		4,385
Total lease cost	$	247,101	$	213,511	$	178,628

(a)     Primarily relates to purchased power lease contracts.

The following tables provide other additional information related to operating lease liabilities (dollars in thousands):

	Year Ended December 31, 2021		Year Ended December 31, 2020		Year Ended December 31, 2019
Cash paid for amounts included in the measurement of lease liabilities — operating cash flows:	$	116,661	$	75,097	$	69,075
Right-of-use operating lease assets obtained in exchange for operating lease liabilities	500,582		441,653		11,262

	December 31, 2021		December 31, 2020
Weighted average remaining lease term	8 years		6 years
Weighted average discount rate (a)	2.13	%	1.69	%

(a)Most of our lease agreements do not contain an implicit rate that is readily determinable. For these agreements we use our incremental borrowing rate to measure the present value of lease liabilities. We determine our incremental borrowing rate at lease commencement based on the rate of interest that we would have to pay to borrow, on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. We use the implicit rate when it is readily determinable.

Schedule of maturities of operating lease liabilities

The following table provides information related to the maturity of our operating lease liabilities (dollars in thousands):

	December 31, 2021
Year	Purchased Power Lease Contracts		Land, Property & Equipment Leases		Total
2022	$	103,752	$	13,051	$	116,803
2023	106,151		10,758		116,909
2024	104,315		8,073		112,388
2025	106,582		6,034		112,616
2026	120,016		4,803		124,819
Thereafter	299,594		35,289		334,883
Total lease commitments	840,410		78,008		918,418
Less imputed interest	72,249		17,325		89,574
Total lease liabilities	$	768,161	$	60,683	$	828,844