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
Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss, beginning balance	$ 447,765	$ 304,924
Reduction of credit losses	34,026	248,901
Foreign currency translation adjustments	112	(1,185)
Allowance for credit loss, ending balance	391,751	548,963
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	120,796	67,656
Reduction of credit losses	(16,067)	(5,477)
Foreign currency translation adjustments	21	(315)
Allowance for credit loss, ending balance	104,750	84,690
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	$ 22,826

Amount of gain (loss) from converting allowance reserve for credit loss to currency of reporting entity from amount denominated or measured in a different currency, which decreases (increases) the allowance for loan and lease losses.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of credit loss expense (reversal of expense) for financing receivable.

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