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Related Party Transactions (Details)	1 Months Ended	3 Months Ended		12 Months Ended
Related Party Transactions (Details)	Jan. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) engine aircraft.	Dec. 31, 2018 engine	Dec. 31, 2018 aircraft.	Dec. 31, 2018 USD ($)	Sep. 12, 2018 USD ($) $ / shares
Related Party and Similar Transactions
Maintenance reserve revenue				$ 108,998,000			$ 87,009,000
WMES
Related Party and Similar Transactions
Number of assets sold				5	2	1
Proceeds from sale of assets				$ 76,400,000			30,700,000
Willis Aeronautical Services, Inc.
Related Party and Similar Transactions
Number of assets sold \| engine				1
Proceeds from sale of assets				$ 2,600,000
CASC Willis
Related Party and Similar Transactions
Number of assets sold \| aircraft.				0
Chief Executive Officer
Related Party and Similar Transactions
Number of shares repurchased (in shares)								$ 88,000
Repurchased price (in dollars per share) \| $ / shares								$ 34.2972
Purchase of artwork by CEO			$ 5,000
Amounts related party transaction		$ 450
Mikchalk Lake LLC
Related Party and Similar Transactions
Expenses paid				$ 36,000			44,000
Sale of Vehicle \| Chief Executive Officer
Related Party and Similar Transactions
Amounts related party transaction	$ 100,000
Use of Marine Vessel \| Chief Executive Officer
Related Party and Similar Transactions
Amounts related party transaction				200,000
Asset Management \| WMES \| Other Revenue
Related Party and Similar Transactions
Maintenance reserve revenue				$ 2,900,000			$ 2,600,000