Loans, Allowance for Loan Losses and Allowance for Unfunded Credit Commitments - Allowance for Credit Losses: Unfunded Credit Commitments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss, beginning balance	$ 548,963	$ 300,151	$ 304,924	$ 280,903
Provision for credit losses	51,899	19,148	300,800	44,969
Foreign currency translation adjustments	(52)	(796)	(1,237)	206
Allowance for credit loss, ending balance	589,828	301,888	589,828	301,888
Cumulative adjustment for the adoption of amendment
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss, beginning balance			25,464
Unfunded Credit Commitments
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss, beginning balance	84,690	57,970	67,656	55,183
Provision for credit losses	14,590	4,798	9,113	7,528
Foreign currency translation adjustments	14	(104)	(301)	(47)
Allowance for credit loss, ending balance	99,294	62,664	99,294	62,664
Unfunded Credit Commitments | Cumulative adjustment for the adoption of amendment
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss, beginning balance	$ 0	$ 0	$ 22,826	$ 0