Loans Acquired - Textual (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Apr. 12, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net loans	$ 12,936,959,000		$ 12,936,959,000				$ 11,666,572,000
Loans	13,000,000,000.00		13,000,000,000.00				11,720,000,000
Allowance for loan losses	66,590,000	$ 56,703,000	66,590,000	$ 56,703,000	$ 64,179,000		56,694,000	$ 53,776,000	$ 42,086,000
Provision for loan losses	21,973,000	10,345,000	38,337,000	28,528,000
Loans acquired, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	597,000	1,345,000	597,000	1,345,000	$ 1,112,000		$ 95,000	$ 2,044,000	$ 418,000
Provision for loan losses	$ 0	$ 0	$ 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