Premises and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Depreciation and amortization expense charged	$ 14,100	$ 11,500	$ 10,500
Capitalized right of use asset and lease liabilities to be regcognize upon adoption of ASU	$ 20,000
Weighted-average lease term	15 years 8 months 12 days
Operating lease ROU assets	$ 51,500	53,600
Operating lease ROU liabilities	$ 56,036	$ 56,500
Operating Lease Liability Statement Of Financial Position Extensible List	us-gaap:OtherLiabilities	us-gaap:OtherLiabilities
Operating lease, expense	$ 5,800	$ 5,400	4,500
Weighted average discount rate	2.81%
Weighted-average finance lease term	13 years 6 months
Finance lease ROU assets	$ 4,500	5,000
Finance lease ROU liabilities	$ 5,180	$ 5,600
Weighted average finance lease discount rate	3.78%	3.77%
Amortization cost related to finance lease ROU assets	$ 400	$ 400	400
Interest expense related to finance lease ROU assets	$ 200	200	$ 200
Old Line Bancshares, Inc. [Member]
Property Plant And Equipment [Line Items]
Operating lease ROU assets		37,200
Operating lease ROU liabilities		$ 37,200
Maximum [Member]
Property Plant And Equipment [Line Items]
Operating lease terms	30 years
Operating lease term extensions	10 years
Finance lease terms	20 years
Finance lease term extensions	10 years
Minimum [Member]
Property Plant And Equipment [Line Items]
Operating lease terms	1 year
Operating lease term extensions	5 years
Finance lease terms	5 years
Finance lease term extensions	5 years