Investment Securities - Amortized Cost and Fair Values of Debt Securities Held to Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 393,855	$ 422,096
Gross Unrealized Gains	387	345
Gross Unrealized Losses	(10,249)	(4,192)
Estimated Fair Value	383,993	418,249
Obligations of U.S. Government-Sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	42,331	40,540
Gross Unrealized Gains	175	335
Gross Unrealized Losses	(313)	(161)
Estimated Fair Value	42,193	40,714
ERROR in label resolution.
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	400	200
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	400	200
Mortgage - Backed Securities - Commercial [Member] \| Obligations of U.S. Government [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	55,221	58,249
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2,327)	(1,394)
Estimated Fair Value	52,894	56,855
Mortgage - Backed Securities - Commercial [Member] \| Obligations of U.S. Government-Sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	13,159	14,056
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(258)	(71)
Estimated Fair Value	12,901	13,985
Mortgage - Backed Securities - Residential [Member] \| Obligations of U.S. Government [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3,635	3,925
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(97)	(14)
Estimated Fair Value	3,538	3,911
Mortgage - Backed Securities - Residential [Member] \| Obligations of U.S. Government-Sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	279,109	305,126
Gross Unrealized Gains	212	10
Gross Unrealized Losses	(7,254)	(2,552)
Estimated Fair Value	$ 272,067	$ 302,584

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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

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

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