Loans Receivable and Allowance for Credit Losses (Allowance for Credit Losses Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses
Allowance for loan losses	$ 619,983	$ 358,287	$ 311,322		$ 287,128
Increase to allowance for loan losses	261,700
Provision for credit losses	210,653	98,685	64,255
Gross charge-offs	$ 81,837	$ 75,067	$ 59,433
Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Losses
Allowance for loan losses				$ 125,200