Disclosures About Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	$ 765,579	$ 819,901
Derivative assets	55,360	21,593
Interest rate swaps	55,496	20,991
Level 1
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	0	0
Total financial assets	301,985	86,601
Level 2
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	765,579	819,901
Total financial assets	838,400	859,158
Level 3
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	0	0
Total financial assets	8,758,412	8,674,417
Measured on recurring basis
Assets and liabilities measured at fair value on a recurring basis
Derivative assets		20,889
Total financial assets	820,939	841,494
Total liabilities	55,496	20,991
Measured on recurring basis | Level 1
Assets and liabilities measured at fair value on a recurring basis
Derivative assets		0
Total financial assets	0	0
Total liabilities	0	0
Measured on recurring basis | Level 2
Assets and liabilities measured at fair value on a recurring basis
Derivative assets		20,889
Total financial assets	820,432	840,935
Total liabilities	55,496	20,991
Measured on recurring basis | Level 3
Assets and liabilities measured at fair value on a recurring basis
Derivative assets		0
Total financial assets	507	559
Total liabilities	0	0
Debt securities | Measured on recurring basis
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	124,866	146,742
Debt securities | Measured on recurring basis | U.S. government and agencies
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale		14,991
Debt securities | Measured on recurring basis | Government sponsored enterprises
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	80,169	104,784
Debt securities | Measured on recurring basis | States and political subdivisions
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	44,697	26,048
Debt securities | Measured on recurring basis | Corporate
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale		919
Debt securities | Measured on recurring basis | Level 1
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	0	0
Debt securities | Measured on recurring basis | Level 1 | U.S. government and agencies
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale		0
Debt securities | Measured on recurring basis | Level 1 | Government sponsored enterprises
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	0	0
Debt securities | Measured on recurring basis | Level 1 | States and political subdivisions
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	0	0
Debt securities | Measured on recurring basis | Level 1 | Corporate
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale		0
Debt securities | Measured on recurring basis | Level 2
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	124,866	146,742
Debt securities | Measured on recurring basis | Level 2 | U.S. government and agencies
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale		14,991
Debt securities | Measured on recurring basis | Level 2 | Government sponsored enterprises
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	80,169	104,784
Debt securities | Measured on recurring basis | Level 2 | States and political subdivisions
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	44,697	26,048
Debt securities | Measured on recurring basis | Level 2 | Corporate
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale		919
Debt securities | Measured on recurring basis | Level 3
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	0	0
Debt securities | Measured on recurring basis | Level 3 | U.S. government and agencies
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale		0
Debt securities | Measured on recurring basis | Level 3 | Government sponsored enterprises
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	0	0
Debt securities | Measured on recurring basis | Level 3 | States and political subdivisions
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	0	0
Debt securities | Measured on recurring basis | Level 3 | Corporate
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale		0
Total mortgage-backed securities | Measured on recurring basis
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	640,713	673,159
Total mortgage-backed securities | Measured on recurring basis | Level 1
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Total mortgage-backed securities | Measured on recurring basis | Level 2
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	640,713	673,159
Total mortgage-backed securities | Measured on recurring basis | Level 3
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Residential mortgage-backed securities
Assets and liabilities measured at fair value on a recurring basis
Securities available-for-sale	640,713	673,159
Residential mortgage-backed securities | Measured on recurring basis | GNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	23,167	23,264
Residential mortgage-backed securities | Measured on recurring basis | FNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	81,823	89,259
Residential mortgage-backed securities | Measured on recurring basis | FHLMC
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	48,113	50,139
Residential mortgage-backed securities | Measured on recurring basis | Non-agency
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	489	497
Residential mortgage-backed securities | Measured on recurring basis | Level 1 | GNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Residential mortgage-backed securities | Measured on recurring basis | Level 1 | FNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Residential mortgage-backed securities | Measured on recurring basis | Level 1 | FHLMC
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Residential mortgage-backed securities | Measured on recurring basis | Level 1 | Non-agency
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Residential mortgage-backed securities | Measured on recurring basis | Level 2 | GNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	23,167	23,264
Residential mortgage-backed securities | Measured on recurring basis | Level 2 | FNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	81,823	89,259
Residential mortgage-backed securities | Measured on recurring basis | Level 2 | FHLMC
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	48,113	50,139
Residential mortgage-backed securities | Measured on recurring basis | Level 2 | Non-agency
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	489	497
Residential mortgage-backed securities | Measured on recurring basis | Level 3 | GNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Residential mortgage-backed securities | Measured on recurring basis | Level 3 | FNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Residential mortgage-backed securities | Measured on recurring basis | Level 3 | FHLMC
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Residential mortgage-backed securities | Measured on recurring basis | Level 3 | Non-agency
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Collateralized mortgage obligations | Measured on recurring basis | GNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	202,997	207,016
Collateralized mortgage obligations | Measured on recurring basis | FNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	175,080	184,682
Collateralized mortgage obligations | Measured on recurring basis | FHLMC
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	109,044	118,302
Collateralized mortgage obligations | Measured on recurring basis | Level 1 | GNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Collateralized mortgage obligations | Measured on recurring basis | Level 1 | FNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Collateralized mortgage obligations | Measured on recurring basis | Level 1 | FHLMC
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Collateralized mortgage obligations | Measured on recurring basis | Level 2 | GNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	202,997	207,016
Collateralized mortgage obligations | Measured on recurring basis | Level 2 | FNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	175,080	184,682
Collateralized mortgage obligations | Measured on recurring basis | Level 2 | FHLMC
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	109,044	118,302
Collateralized mortgage obligations | Measured on recurring basis | Level 3 | GNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Collateralized mortgage obligations | Measured on recurring basis | Level 3 | FNMA
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Collateralized mortgage obligations | Measured on recurring basis | Level 3 | FHLMC
Assets and liabilities measured at fair value on a recurring basis
Residential mortgage-backed securities:	0	0
Interest rate lock commitments | Measured on recurring basis
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	507	559
Interest rate lock commitments | Measured on recurring basis | Level 1
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	0	0
Interest rate lock commitments | Measured on recurring basis | Level 2
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	0	0
Interest rate lock commitments | Measured on recurring basis | Level 3
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	507	559
Forward commitments | Measured on recurring basis
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	197	145
Forward commitments | Measured on recurring basis | Level 1
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	0	0
Forward commitments | Measured on recurring basis | Level 2
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	197	145
Forward commitments | Measured on recurring basis | Level 3
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	0	0
Interest rate swaps | Measured on recurring basis
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	54,656
Interest rate swaps	55,376	20,952
Interest rate swaps | Measured on recurring basis | Level 1
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	0
Interest rate swaps	0	0
Interest rate swaps | Measured on recurring basis | Level 2
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	54,656
Interest rate swaps	55,376	20,952
Interest rate swaps | Measured on recurring basis | Level 3
Assets and liabilities measured at fair value on a recurring basis
Derivative assets	0
Interest rate swaps	0	0
Risk participation agreements | Measured on recurring basis
Assets and liabilities measured at fair value on a recurring basis
Interest rate swaps	120	39
Risk participation agreements | Measured on recurring basis | Level 1
Assets and liabilities measured at fair value on a recurring basis
Interest rate swaps	0	0
Risk participation agreements | Measured on recurring basis | Level 2
Assets and liabilities measured at fair value on a recurring basis
Interest rate swaps	120	39
Risk participation agreements | Measured on recurring basis | Level 3
Assets and liabilities measured at fair value on a recurring basis
Interest rate swaps	$ 0	$ 0