Securities Available for Sale and Held to Maturity - Securities Held to Maturity by Credit Rating, as Determined by Moody's (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Held to Maturity Amortized Cost	$ 394,905	$ 538,072
Aaa [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Held to Maturity Amortized Cost	384,222	511,488
Aaa1 to Aa3 [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Held to Maturity Amortized Cost	7,510	22,528
Not Rated [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities Held to Maturity Amortized Cost	$ 3,173	$ 4,056

Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919253-210447

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953401-111524

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27232-111563

Name:	us-gaap_HeldToMaturitySecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant