Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Data [Abstract]
Interest income	$ 38,411	$ 39,542	$ 43,621	$ 46,107	$ 46,960	$ 49,573	$ 48,388	$ 48,468	$ 167,681	$ 193,389	$ 181,055
Interest expense	3,374	4,510	6,236	9,774	10,975	12,175	11,777	10,821	23,894	45,748	31,584
Net interest income	35,037	35,032	37,385	36,333	35,985	37,398	36,611	37,647	143,787	147,641	149,471
Provision for credit losses	(1,209)	4,101	3,435	35,350	2,404	966	1,610	3,615	41,677	8,595	7,089
Noninterest Income	22,006	21,099	20,566	18,300	23,255	19,455	20,221	19,253	81,971	82,184	75,982
Noninterest expense	38,624	35,197	35,503	33,403	36,251	35,126	35,205	39,845	142,727	146,427	140,407
Income before income taxes	19,628	16,833	19,013	(14,120)	20,585	20,761	20,017	13,440	41,354	74,803	77,957
Income tax (benefit) expense	4,094	3,709	4,010	(2,957)	4,202	4,402	4,239	2,764	8,856	15,607	14,165
Net income	15,534	13,124	15,003	(11,163)	16,383	16,359	15,778	10,676	32,498	59,196	63,792
Net loss attributable to noncontrolling interest	(3)	(40)	(32)	0	(1)	(1)	(7)	(1)	(75)	(10)	0
Net income attributable to Bryn Mawr Bank Corporation	$ 15,537	$ 13,164	$ 15,035	$ (11,163)	$ 16,384	$ 16,360	$ 15,785	$ 10,677	$ 32,573	$ 59,206	$ 63,792
Basic earnings per common share (in dollars per share)	$ 0.78	$ 0.66	$ 0.75	$ (0.56)	$ 0.81	$ 0.81	$ 0.78	$ 0.53	$ 1.63	$ 2.94	$ 3.15
Diluted earnings per common share (in dollars per share)	0.78	0.66	0.75	(0.56)	0.81	0.81	0.78	0.53	1.63	2.93	3.13
Dividends declared per share (in dollars per share)	$ 0.27	$ 0.27	$ 0.26	$ 0.26	$ 0.26	$ 0.26	$ 0.25	$ 0.25	$ 1.06	$ 1.02	$ 0.94