Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)		12 Months Ended
	Nov. 22, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Intangible Assets Goodwill And Other Assets [Line Items]
Goodwill		$ 1,100,000,000	$ 1,100,000,000
Other intangible assets		66,329,000	80,433,000
Amortization of core deposit and customer list intangible assets		13,400,000	$ 10,100,000	$ 6,400,000
Goodwill, impairment loss		0
Old Line Bancshares, Inc. [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Goodwill acquired	$ 231,814,000	231,800,000
Old Line Bancshares, Inc. [Member] | Core Deposits [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Intangible assets acquired		$ 32,900,000
Minimum [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Intangible asset, useful life		10 years
Maximum [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Intangible asset, useful life		16 years