Securities (Amortized Cost and Fair Value of Debt Securities Held to Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	$ 1,375,342	$ 1,357,170
Securities Held to Maturity, Gross Unrealized Gains	81,693	110,413
Securities Held to Maturity, Gross Unrealized Losses	1,811	2
Securities Held to Maturity, Fair Value	1,455,224	1,467,581
Municipal Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	624,649	627,019
Securities Held to Maturity, Gross Unrealized Gains	42,623	51,408
Securities Held to Maturity, Gross Unrealized Losses	311	2
Securities Held to Maturity, Fair Value	666,961	678,425
Residential Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	53,298	21,951
Securities Held to Maturity, Gross Unrealized Gains	1,315	1,469
Securities Held to Maturity, Gross Unrealized Losses	459
Securities Held to Maturity, Fair Value	54,154	23,420
Commercial Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	574,923	549,686
Securities Held to Maturity, Gross Unrealized Gains	35,164	54,587
Securities Held to Maturity, Gross Unrealized Losses	1,041
Securities Held to Maturity, Fair Value	609,046	604,273
Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	122,472	158,514
Securities Held to Maturity, Gross Unrealized Gains	2,591	2,949
Securities Held to Maturity, Fair Value	$ 125,063	$ 161,463

Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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- Definition

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

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- Definition

Amount, before other-than-temporary impairment (OTTI) accretion, of investment in debt securities measured at amortized cost (held-to-maturity).

+ References

No definition available.

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- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=SL120269820-111563

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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