Loans - Days past due and Non-accruing (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other information concerning the credit quality
Total Gross Loans	$ 8,733,570	$ 8,852,005
Non-accruing	8,650	4,857
Current
Other information concerning the credit quality
Current	8,714,321	8,839,152
30-59
Other information concerning the credit quality
Days Past Due	2,106	7,046
60-89
Other information concerning the credit quality
Days Past Due	10,583	1,242
90
Other information concerning the credit quality
Days Past Due	6,560	4,565
Business Loans | Commercial and industrial
Other information concerning the credit quality
Total Gross Loans	1,265,185	1,364,461
Non-accruing	4,637	931
Business Loans | Franchise
Other information concerning the credit quality
Total Gross Loans	916,875	765,416
Non-accruing	0	190
Business Loans | Commercial owner occupied
Other information concerning the credit quality
Total Gross Loans	1,674,092	1,679,122
Non-accruing	0	599
Business Loans | SBA
Other information concerning the credit quality
Total Gross Loans	177,487	198,201
Non-accruing	2,519	2,739
Business Loans | Agribusiness
Other information concerning the credit quality
Total Gross Loans	127,834
Non-accruing	0
Business Loans | Warehouse Facilities
Other information concerning the credit quality
Total Gross Loans		138,519
Non-accruing		0
Business Loans | Current | Commercial and industrial
Other information concerning the credit quality
Current	1,260,940	1,362,017
Business Loans | Current | Franchise
Other information concerning the credit quality
Current	907,733	759,546
Business Loans | Current | Commercial owner occupied
Other information concerning the credit quality
Current	1,673,761	1,677,967
Business Loans | Current | SBA
Other information concerning the credit quality
Current	174,271	195,051
Business Loans | Current | Agribusiness
Other information concerning the credit quality
Current	127,834
Business Loans | Current | Warehouse Facilities
Other information concerning the credit quality
Current		138,519
Business Loans | 30-59 | Commercial and industrial
Other information concerning the credit quality
Days Past Due	422	309
Business Loans | 30-59 | Franchise
Other information concerning the credit quality
Days Past Due	0	5,680
Business Loans | 30-59 | Commercial owner occupied
Other information concerning the credit quality
Days Past Due	331	343
Business Loans | 30-59 | SBA
Other information concerning the credit quality
Days Past Due	169	524
Business Loans | 30-59 | Agribusiness
Other information concerning the credit quality
Days Past Due	0
Business Loans | 30-59 | Warehouse Facilities
Other information concerning the credit quality
Days Past Due		0
Business Loans | 60-89 | Commercial and industrial
Other information concerning the credit quality
Days Past Due	826	1,204
Business Loans | 60-89 | Franchise
Other information concerning the credit quality
Days Past Due	9,142	0
Business Loans | 60-89 | Commercial owner occupied
Other information concerning the credit quality
Days Past Due	0	0
Business Loans | 60-89 | SBA
Other information concerning the credit quality
Days Past Due	613	0
Business Loans | 60-89 | Agribusiness
Other information concerning the credit quality
Days Past Due	0
Business Loans | 60-89 | Warehouse Facilities
Other information concerning the credit quality
Days Past Due		0
Business Loans | 90 | Commercial and industrial
Other information concerning the credit quality
Days Past Due	2,997	931
Business Loans | 90 | Franchise
Other information concerning the credit quality
Days Past Due	0	190
Business Loans | 90 | Commercial owner occupied
Other information concerning the credit quality
Days Past Due	0	812
Business Loans | 90 | SBA
Other information concerning the credit quality
Days Past Due	2,434	2,626
Business Loans | 90 | Agribusiness
Other information concerning the credit quality
Days Past Due	0
Business Loans | 90 | Warehouse Facilities
Other information concerning the credit quality
Days Past Due		0
Real Estate Loans | Commercial non-owner occupied
Other information concerning the credit quality
Total Gross Loans	2,072,374	2,004,536
Non-accruing	1,128	0
Real Estate Loans | Multi-family
Other information concerning the credit quality
Total Gross Loans	1,576,870	1,535,289
Non-accruing	0	0
Real Estate Loans | One-to-four family
Other information concerning the credit quality
Total Gross Loans	254,779	356,264
Non-accruing	366	398
Real Estate Loans | Construction
Other information concerning the credit quality
Total Gross Loans	410,065	523,643
Non-accruing	0	0
Real Estate Loans | Farmland
Other information concerning the credit quality
Total Gross Loans	175,997	150,502
Non-accruing	0	0
Real Estate Loans | Land
Other information concerning the credit quality
Total Gross Loans	31,090	46,628
Non-accruing	0	0
Real Estate Loans | Current | Commercial non-owner occupied
Other information concerning the credit quality
Current	2,070,067	2,004,536
Real Estate Loans | Current | Multi-family
Other information concerning the credit quality
Current	1,576,870	1,535,275
Real Estate Loans | Current | One-to-four family
Other information concerning the credit quality
Current	254,779	356,219
Real Estate Loans | Current | Construction
Other information concerning the credit quality
Current	410,065	523,643
Real Estate Loans | Current | Farmland
Other information concerning the credit quality
Current	175,997	150,502
Real Estate Loans | Current | Land
Other information concerning the credit quality
Current	31,090	46,628
Real Estate Loans | 30-59 | Commercial non-owner occupied
Other information concerning the credit quality
Days Past Due	1,179	0
Real Estate Loans | 30-59 | Multi-family
Other information concerning the credit quality
Days Past Due	0	14
Real Estate Loans | 30-59 | One-to-four family
Other information concerning the credit quality
Days Past Due	0	30
Real Estate Loans | 30-59 | Construction
Other information concerning the credit quality
Days Past Due	0	0
Real Estate Loans | 30-59 | Farmland
Other information concerning the credit quality
Days Past Due	0	0
Real Estate Loans | 30-59 | Land
Other information concerning the credit quality
Days Past Due	0	0
Real Estate Loans | 60-89 | Commercial non-owner occupied
Other information concerning the credit quality
Days Past Due	0	0
Real Estate Loans | 60-89 | Multi-family
Other information concerning the credit quality
Days Past Due	0	0
Real Estate Loans | 60-89 | One-to-four family
Other information concerning the credit quality
Days Past Due	0	9
Real Estate Loans | 60-89 | Construction
Other information concerning the credit quality
Days Past Due	0	0
Real Estate Loans | 60-89 | Farmland
Other information concerning the credit quality
Days Past Due	0	0
Real Estate Loans | 60-89 | Land
Other information concerning the credit quality
Days Past Due	0	0
Real Estate Loans | 90 | Commercial non-owner occupied
Other information concerning the credit quality
Days Past Due	1,128	0
Real Estate Loans | 90 | Multi-family
Other information concerning the credit quality
Days Past Due	0	0
Real Estate Loans | 90 | One-to-four family
Other information concerning the credit quality
Days Past Due	0	6
Real Estate Loans | 90 | Construction
Other information concerning the credit quality
Days Past Due	0	0
Real Estate Loans | 90 | Farmland
Other information concerning the credit quality
Days Past Due	0	0
Real Estate Loans | 90 | Land
Other information concerning the credit quality
Days Past Due	0	0
Consumer Loans | Consumer loans
Other information concerning the credit quality
Total Gross Loans	50,922	89,424
Non-accruing	0	0
Consumer Loans | Current | Consumer loans
Other information concerning the credit quality
Current	50,914	89,249
Consumer Loans | 30-59 | Consumer loans
Other information concerning the credit quality
Days Past Due	5	146
Consumer Loans | 60-89 | Consumer loans
Other information concerning the credit quality
Days Past Due	2	29
Consumer Loans | 90 | Consumer loans
Other information concerning the credit quality
Days Past Due	$ 1	$ 0