Preparation of Interim Financial Statements (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2019 USD ($) financial_center	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) financial_center	Sep. 30, 2018 USD ($)	Apr. 11, 2019 financial_center	Jan. 01, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Number of financial centers | financial_center	212			212
Unrealized holding gain on the transfer of held-to-maturity securities to available-for-sale per ASU 2017-12	$ 0		$ 0	$ 2,547	$ 0
Right-of-use asset	34,100			34,100
Right-of-use liabilities	34,300			34,300
Accounting Standards Update 2018-15
Lessee, Lease, Description [Line Items]
Software implementation costs, not yet capitalized	$ 1,100			$ 1,100
Accounting Standards Update 2017-12
Lessee, Lease, Description [Line Items]
Fair value of HTM municipal bonds		$ 216,400
Unrealized holding gain on the transfer of held-to-maturity securities to available-for-sale per ASU 2017-12		$ 2,500
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Right-of-use asset							$ 32,800
Right-of-use liabilities							$ 32,800
Minimum | Accounting Standards Update 2016-13
Lessee, Lease, Description [Line Items]
Allowance for loan and lease losses, period increase, percent				130.00%
AllowAllowance for loan and lease losses including purchase discounts, period increase, percent				10.00%
Maximum | Accounting Standards Update 2016-13
Lessee, Lease, Description [Line Items]
Allowance for loan and lease losses, period increase, percent				170.00%
AllowAllowance for loan and lease losses including purchase discounts, period increase, percent				30.00%
Reliance Bancshares, Inc.
Lessee, Lease, Description [Line Items]
Number of financial centers | financial_center						22
Reliance Bancshares, Inc. | Minimum | Accounting Standards Update 2016-13
Lessee, Lease, Description [Line Items]
Allowance for loan and lease losses, period increase, percent				165.00%
AllowAllowance for loan and lease losses including purchase discounts, period increase, percent				5.00%
Reliance Bancshares, Inc. | Maximum | Accounting Standards Update 2016-13
Lessee, Lease, Description [Line Items]
Allowance for loan and lease losses, period increase, percent				215.00%
AllowAllowance for loan and lease losses including purchase discounts, period increase, percent				25.00%