Summary of Significant Accounting Policies (Details) $ in Millions			1 Months Ended	12 Months Ended
	Nov. 13, 2018 USD ($) branch shares	Feb. 08, 2018	Feb. 28, 2018	Dec. 31, 2018 USD ($) financial_center segment shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of financial centers | financial_center				191
Number of reportable segments | segment				1
Derivative asset, notional amount				$ 561.3	$ 303.5
Stock split, conversion ratio		2	2
Scenario, Plan | Reliance Bancshares, Inc.
Business Acquisition [Line Items]
Equity interest issued or issuable (in shares) | shares	4,000,000
Payments to acquire businesses, gross	$ 62.7
Number of bank branches | branch	20
Assets acquired	$ 1,500.0
Loans acquired	1,100.0
Deposits acquired	$ 1,200.0
Series A Preferred Stock | Scenario, Plan | Reliance Bancshares, Inc.
Business Acquisition [Line Items]
Conversion ratio	1
Series B Preferred Stock | Scenario, Plan | Reliance Bancshares, Inc.
Business Acquisition [Line Items]
Conversion ratio	1
Series C Preferred Stock | Scenario, Plan | Reliance Bancshares, Inc.
Business Acquisition [Line Items]
Conversion ratio	1
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares) | shares				0	0	0