Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)		12 Months Ended
	Nov. 22, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets Goodwill And Other Assets [Line Items]
Goodwill		$ 1,100,000,000	$ 900,000,000
Other intangible assets		80,433,000	56,966,000
Amortization of core deposit and customer list intangible assets		10,100,000	6,400,000	$ 4,100,000
Goodwill, impairment loss		0
Amortization of intangible assets		10,340,000	6,980,000	4,940,000
Old Line Bancshares, Inc. [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Goodwill acquired	$ 203,774,000	203,800,000
Old Line Bancshares, Inc. [Member] | Core Deposits [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Intangible assets acquired		33,600,000
YCB and ESB [Member] | Noncompete Agreements [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Amortization of intangible assets		$ 200,000	$ 600,000	$ 900,000
Minimum [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Intangible asset, useful life		10 years
Minimum [Member] | YCB and ESB [Member] | Noncompete Agreements [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Intangible asset, useful life		1 year
Maximum [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Intangible asset, useful life		16 years
Maximum [Member] | YCB and ESB [Member] | Noncompete Agreements [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Intangible asset, useful life		4 years