Nature of Operations and Basis of Presentation (Variable Interest Entities) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($) variable_interest_entity	Dec. 31, 2019 USD ($)
Variable Interest Entity [Line Items]
Number of variable interest entities | variable_interest_entity	1
Fair value of VIE	$ 3,048,480	$ 3,013,472
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Fair value of VIE	$ 3,638