Investment in Other Companies (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Long-term debt	$ 2,964,951	$ 3,203,696
Aero Engines, LLC.
Payments to acquire interest in joint venture			$ 22,300
Investment ownership (as a percent)		75.00%	75.00%
Additional interest in Joint venture		$ 1,000
Long-term debt	0
Aero Engines, LLC. \| Other Assets
Investment balance in Aero Engines	19,700
Aero Engines, LLC. \| Other Nonoperating Income.
Company's portion of income generated by Aero Engines	$ 5,800

Amount of payments to acquire additional interest in Joint venture.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The cash outflow associated with the investment in or advances to an entity in which the reporting entity shares control of the entity with another party or group.

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