Other Assets - Goodwill (Details) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)
Goodwill
Number of reporting segments with goodwill \| segment	2	2
Goodwill	$ 995,492	$ 995,492
Impairment of goodwill	0	0	$ 0
Retail Banking
Goodwill
Goodwill	687,492	687,492
Commercial Banking
Goodwill
Goodwill	$ 308,000	$ 308,000

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Name:	us-gaap_GoodwillImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration