Selected Quarterly Financial Data (Unaudited) - Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Interest income	$ 47,534	$ 45,233	$ 44,754	$ 43,534	$ 34,798	$ 33,198	$ 31,237	$ 30,326	$ 181,055	$ 129,559	$ 116,991
Interest expense	9,547	8,504	7,438	6,095	4,477	3,760	3,272	2,923	31,584	14,432	10,755
Net interest income	37,987	36,729	37,316	37,439	30,321	29,438	27,965	27,403	149,471	115,127	106,236
Provision for loan and lease losses	2,362	664	3,137	1,030	1,077	1,333	(83)	291	7,193	2,618	4,326
Total noninterest income	18,097	18,274	20,075	19,536	15,536	15,584	14,785	13,227	75,982	59,132	53,968
Noninterest expense	34,845	33,592	35,836	36,030	31,056	28,184	28,495	26,660	140,303	114,395	101,674
Income before income taxes	18,877	20,747	18,418	19,915	13,724	15,505	14,338	13,679	77,957	57,246	54,204
Income tax expense	1,746	4,066	3,723	4,630	19,924	4,766	4,905	4,635	14,165	34,230	18,168
Net income	17,131	16,681	14,695	15,285	(6,200)	10,739	9,433	9,044	63,792	23,016	36,036
Net (loss) income attributable to noncontrolling interest	(5)	(1)	7	(1)	0	0	0	0	0	0	0
Net income attributable to Bryn Mawr Bank Corporation	$ 17,136	$ 16,682	$ 14,688	$ 15,286	$ (6,200)	$ 10,739	$ 9,433	$ 9,044	$ 63,792	$ 23,016	$ 36,036
Basic earnings per common share (in dollars per share)	$ 0.85	$ 0.82	$ 0.73	$ 0.76	$ (0.35)	$ 0.63	$ 0.56	$ 0.53	$ 3.15	$ 1.34	$ 2.14
Diluted earnings per common share (in dollars per share)	0.84	0.82	0.72	0.75	(0.35)	0.62	0.55	0.53	3.13	1.32	2.12
Dividends declared per share (in dollars per share)	$ 0.25	$ 0.25	$ 0.22	$ 0.22	$ 0.22	$ 0.22	$ 0.21	$ 0.21	$ 0.94	$ 0.86	$ 0.82