Securities (Securities Held to Maturity with Unrealized Losses) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Losses less than 12 months, Fair Value	$ 3,027	$ 401,593
Held to Maturity, Losses less than 12 months, Gross Unrealized Losses	27	2,660
Held to Maturity, Losses 12 months or longer, Fair Value	789,533	1,720,624
Held to Maturity, Losses 12 months or longer, Gross Unrealized Losses	5,417	46,813
Held to Maturity, Total, Fair Value	792,560	2,122,217
Held to Maturity, Total, Gross Unrealized Losses	5,444	49,473
U.S. Treasury And Government Agency Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Losses 12 months or longer, Fair Value	49,881	49,521
Held to Maturity, Losses 12 months or longer, Gross Unrealized Losses	119	478
Held to Maturity, Total, Fair Value	49,881	49,521
Held to Maturity, Total, Gross Unrealized Losses	119	478
Municipal Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Losses less than 12 months, Fair Value	3,027	233,469
Held to Maturity, Losses less than 12 months, Gross Unrealized Losses	27	2,256
Held to Maturity, Losses 12 months or longer, Fair Value	18,972	233,280
Held to Maturity, Losses 12 months or longer, Gross Unrealized Losses	59	7,247
Held to Maturity, Total, Fair Value	21,999	466,749
Held to Maturity, Total, Gross Unrealized Losses	86	9,503
Residential Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Losses less than 12 months, Fair Value		90,730
Held to Maturity, Losses less than 12 months, Gross Unrealized Losses		123
Held to Maturity, Losses 12 months or longer, Fair Value	177,953	235,251
Held to Maturity, Losses 12 months or longer, Gross Unrealized Losses	791	5,994
Held to Maturity, Total, Fair Value	177,953	325,981
Held to Maturity, Total, Gross Unrealized Losses	791	6,117
Commercial Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Losses 12 months or longer, Fair Value	74,946	305,419
Held to Maturity, Losses 12 months or longer, Gross Unrealized Losses	619	10,882
Held to Maturity, Total, Fair Value	74,946	305,419
Held to Maturity, Total, Gross Unrealized Losses	619	10,882
Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity, Losses less than 12 months, Fair Value		77,394
Held to Maturity, Losses less than 12 months, Gross Unrealized Losses		281
Held to Maturity, Losses 12 months or longer, Fair Value	467,781	897,153
Held to Maturity, Losses 12 months or longer, Gross Unrealized Losses	3,829	22,212
Held to Maturity, Total, Fair Value	467,781	974,547
Held to Maturity, Total, Gross Unrealized Losses	$ 3,829	$ 22,493

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for 12 months or longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

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

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for less than 12 months.

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