Securities (Amortized Cost and Fair Value of Securities Held to Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	$ 1,480,494	$ 1,568,009
Securities Held to Maturity, Gross Unrealized Gains	82,105	44,103
Securities Held to Maturity, Gross Unrealized Losses	22	1,108
Securities Held to Maturity, Fair Value	1,562,577	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	627,185	641,019
Securities Held to Maturity, Gross Unrealized Gains	29,093	27,146
Securities Held to Maturity, Gross Unrealized Losses	20	69
Securities Held to Maturity, Fair Value	656,258	668,096
Residential Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	28,236	29,687
Securities Held to Maturity, Gross Unrealized Gains	1,309	883
Securities Held to Maturity, Fair Value	29,545	30,570
Commercial Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	538,865	539,371
Securities Held to Maturity, Gross Unrealized Gains	41,782	12,474
Securities Held to Maturity, Gross Unrealized Losses		581
Securities Held to Maturity, Fair Value	580,647	551,264
Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Securities Held to Maturity, Gross Amortized Cost	286,208	307,932
Securities Held to Maturity, Gross Unrealized Gains	9,921	3,597
Securities Held to Maturity, Gross Unrealized Losses	2	458
Securities Held to Maturity, Fair Value	$ 296,127	$ 311,071

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

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 (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563

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- Definition

Amount of accumulated unrealized loss on 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 (c)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563

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

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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=118939692&loc=d3e27232-111563

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