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Securities, Held to Maturity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	$ 599,164		$ 599,164		$ 630,074
Unrealized gains	23,868		23,868		11,817
Unrealized losses	10		10		629
Estimated fair value	623,022		623,022		641,262
Allowance for credit losses on HTM securities	0		0
Gains from calls on HTM securities	4	$ 0	4	$ 0
Held-to-maturity securities sold, amortized cost	1,000	$ 0	1,000	$ 0
Held-to-maturity securities sold, unrealized loss	1		1
Amortized costs of securities available for sale and held to maturity pledged	1,300,000		1,300,000		1,300,000
Amortized costs of securities AFS and HTM pledged as collateral for repurchase agreements	249,800		249,800		189,800
Mortgage-Backed, Government Sponsored Enterprises [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	144,556		144,556		149,448
Unrealized gains	5,886		5,886		3,184
Unrealized losses	0		0		155
Estimated fair value	150,442		150,442		152,477
Mortgage-Backed, U.S. Government Agency Securities [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	12,220		12,220		13,667
Unrealized gains	938		938		584
Unrealized losses	0		0		0
Estimated fair value	13,158		13,158		14,251
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	145,235		145,235		189,402
Unrealized gains	5,445		5,445		2,165
Unrealized losses	0		0		368
Estimated fair value	150,680		150,680		191,199
Collateralized Mortgage Obligations, U.S. Government Agency Securities [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	105,862		105,862		110,498
Unrealized gains	5,447		5,447		3,256
Unrealized losses	0		0		100
Estimated fair value	111,309		111,309		113,654
State & Municipal [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	191,291		191,291		167,059
Unrealized gains	6,152		6,152		2,628
Unrealized losses	10		10		6
Estimated fair value	$ 197,433		$ 197,433		$ 169,681

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This represents the amortized costs of securities available for sale and held to maturity that are pledged as collateral for securities sold under repurchase agreements.

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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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