Loans Acquired - Textual (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Apr. 12, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net loans	$ 13,063,946,000		$ 13,063,946,000				$ 11,666,572,000
Loans	13,130,000,000		13,130,000,000				11,720,000,000
Allowance for loan losses	64,179,000	$ 53,776,000	64,179,000	$ 53,776,000		$ 60,555,000	56,694,000	$ 47,614,000	$ 42,086,000
Provision for loan losses	7,079,000	9,033,000	16,364,000	18,183,000
Loans acquired, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	1,112,000	2,044,000	1,112,000	2,044,000		$ 1,312,000	$ 95,000	$ 407,000	$ 418,000
Provision for loan losses	$ 0	$ 1,769,000	$ 2,464,000	$ 1,837,000
Reliance Bancshares, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net loans					$ 1,100,000,000
Accounting Standards Update 2017-08 | Reliance Bancshares, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net loans					1,097,000,000.000
Loans					1,127,000,000
Allowance for loan losses					30,600,000
Accounting Standards Update 2016-13 | Reliance Bancshares, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net loans					176,000
Loans					385,000
Allowance for loan losses					$ 209,000