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	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Allowance for unfunded credit reserves
Allowance for unfunded credit commitments, beginning of period			$ 33,500
(Reversal of) provision for credit losses	$ (15,000)	$ 102,443	(15,000)	$ 176,313
Allowance for unfunded credit commitments, end of period	26,200		26,200
Unfunded Credit Commitments
Allowance for unfunded credit reserves
Allowance for unfunded credit commitments, beginning of period	32,529	20,829	33,577	11,158
(Reversal of) provision for credit losses	(6,229)	8,143	(7,277)	7,357
Allowance for unfunded credit commitments, end of period	26,300	28,972	26,300	28,972
Cumulative Effect, Period Of Adoption, Adjustment
Allowance for unfunded credit reserves
Allowance for unfunded credit commitments, beginning of period	$ 0	$ 0	$ 0	$ 10,457