Loans Receivable and Allowance for Credit Losses (Summary of Activities in Allowance for loan losses by Portfolio Segments and Unfunded Credit Commitments) (Details) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member	us-gaap:AccountingStandardsUpdate201613Member
Allowance for unfunded credit reserves
Allowance for unfunded credit commitments, beginning of period		$ 11,100
Provision for credit losses		210,653	$ 98,685	$ 64,255
Allowance for unfunded credit commitments, end of period		33,500	11,100
Unfunded Loan Commitment
Allowance for unfunded credit reserves
Allowance for unfunded credit commitments, beginning of period	$ 12,566	11,158	12,566	13,318
Provision for credit losses		11,962	(1,408)	(752)
Allowance for unfunded credit commitments, end of period		33,577	11,158	12,566
Cumulative Effect, Period of Adoption, Adjustment
Allowance for unfunded credit reserves
Allowance for unfunded credit commitments, beginning of period	$ 0	$ 10,457	0	0
Allowance for unfunded credit commitments, end of period			$ 10,457	$ 0