Commitments - Extensions of Credit (Details) - USD ($) $ in Billions	Jun. 30, 2020	Dec. 31, 2019
Extended lines of credit
Commitments, guarantees:
Unused amounts in lines of credit to third-party entities and commitments for future financing to clients	$ 1.9	$ 1.8
Financing for client purchase agreements
Commitments, guarantees:
Unused amounts in lines of credit to third-party entities and commitments for future financing to clients	$ 5.7	$ 6.3

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