Securities (Amortized Cost and Fair Value of Debt Securities Held to Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	$ 1,408,961	$ 1,568,009
Securities Held to Maturity, Gross Unrealized Gains	108,744	44,103
Securities Held to Maturity, Gross Unrealized Losses	17	1,108
Securities Held to Maturity, Fair Value	1,517,688	1,611,004
U.S. Treasury And Government Agency Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost		50,000
Securities Held to Maturity, Gross Unrealized Gains		3
Securities Held to Maturity, Fair Value		50,003
Municipal Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	630,894	641,019
Securities Held to Maturity, Gross Unrealized Gains	49,348	27,146
Securities Held to Maturity, Gross Unrealized Losses	17	69
Securities Held to Maturity, Fair Value	680,225	668,096
Residential Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	24,041	29,687
Securities Held to Maturity, Gross Unrealized Gains	1,641	883
Securities Held to Maturity, Fair Value	25,682	30,570
Commercial Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	550,201	539,371
Securities Held to Maturity, Gross Unrealized Gains	53,253	12,474
Securities Held to Maturity, Gross Unrealized Losses		581
Securities Held to Maturity, Fair Value	603,454	551,264
Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	203,825	307,932
Securities Held to Maturity, Gross Unrealized Gains	4,502	3,597
Securities Held to Maturity, Gross Unrealized Losses		458
Securities Held to Maturity, Fair Value	$ 208,327	$ 311,071

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

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