Summary of Significant Accounting Policies (New Accounting Standards and Interpretations) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	$ 86,833	$ 106,246	$ 136,589	$ 218,011		$ 3,025	$ 2,271	$ 1,986	$ 1,651	$ 968
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	$ 8,300				$ 8,300
Cumulative Effect, Period of Adoption, Adjustment | Purchased Credit Deteriorated Loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss					$ 62,600