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Related Party Transactions (Details)		3 Months Ended		12 Months Ended
Related Party Transactions (Details)	Dec. 08, 2016 USD ($) $ / shares	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) engine aircraft	Dec. 31, 2017 USD ($) engine	Dec. 31, 2016 USD ($)	Sep. 12, 2018 USD ($) $ / shares	Apr. 01, 2016 USD ($)	Mar. 31, 2016 $ / shares
Related Party and Similar Transactions
Repurchased price \| $ / shares	$ 24.95						$ 34.2972		$ 21.59
Number of shares repurchased	$ 40,000						$ 88,000
Percentage of difference in repurchase and closing price	2.00%
Closing price \| $ / shares	$ 25.46
Revenue				$ 87,009,000	$ 80,189,000	$ 57,091,000
WMES
Related Party and Similar Transactions
Number of engines sold to third party \| engine				2	2
Number of aircraft sold to third party \| aircraft				1
Proceeds from sale of engines and aircraft to third party				$ 30,700,000
Proceeds from sale of engine					$ 14,800,000
WMES \| Other Revenue [Member]
Related Party and Similar Transactions
Revenue				$ 2,600,000	$ 2,400,000	$ 2,100,000
Type of Revenue [Extensible List]				us-gaap:AssetManagement1Member	us-gaap:AssetManagement1Member	us-gaap:AssetManagement1Member
CASC Willis
Related Party and Similar Transactions
Number of engines sold to third party \| engine					1
Proceeds from sale of engine					$ 11,200,000
Chief Executive Officer
Related Party and Similar Transactions
Amounts of utilization and reimbursed		$ 450
Number of shares repurchased								$ 60,000
Purchase of artwork by CEO			$ 5,000
Mikchalk Lake LLC
Related Party and Similar Transactions
Expenses paid				$ 44,000	$ 80,000