Nature of Operations, Basis of Presentation, and Summary of Significant Accounting Policies (Narrative) (Details) - USD ($)	Sep. 30, 2020	Feb. 07, 2020	Dec. 31, 2019
Stifel Credit Facility [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Credit facility	$ 300,000,000.0
North Shore Aviation Holdings LLC [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent			27.50%
North Shore Aviation Holdings LLC [Member] | Stifel Credit Facility [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Credit facility		$ 120,000,000.0