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:	us-gaap_GoodwillImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Goodwill and Other Intangible Assets - Textual (Details) - USD ($)	3 Months Ended					9 Months Ended	12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Goodwill			$ 1,075,305,000			$ 1,075,305,000	$ 1,075,305,000
Goodwill impairment	$ 0	$ 0	$ 0	$ 0	$ 0		$ 0
Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life						10 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life						15 years
Core Deposit Premium \| Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life						10 years
Core Deposit Premium \| Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life						15 years