Business Combinations - Pro Forma Income Statements (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
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total interest income	$ 47,534	$ 45,233	$ 44,754	$ 43,534	$ 34,798	$ 33,198	$ 31,237	$ 30,326	$ 181,055	$ 129,559	$ 116,991
Total 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
Net interest income after provision for loan and lease losses									142,278	112,509	101,910
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
Total noninterest expenses	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 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
Weighted-average basic shares outstanding (in shares)									20,234,792	17,150,125	16,859,623
Dilutive shares (in shares)									155,375	248,798	168,499
Adjusted weighted-average diluted shares (in shares)									20,390,167	17,398,923	17,028,122
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
Pro Forma
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total interest income										$ 171,155	$ 157,276
Total interest expense										20,065	17,086
Net interest income										151,090	140,190
Provision for loan and lease losses										3,454	5,568
Net interest income after provision for loan and lease losses										147,636	134,622
Total noninterest income										61,423	58,275
Total noninterest expenses										140,756	124,261
Income before income taxes										68,303	68,636
Income tax expense										40,841	23,006
Net income attributable to Bryn Mawr Bank Corporation										$ 27,462	$ 45,630
Weighted-average basic shares outstanding (in shares)										20,248,879	19,958,377
Dilutive shares (in shares)										257,591	168,499
Adjusted weighted-average diluted shares (in shares)										20,506,470	20,126,876
Basic earnings per common share (in dollars per share)										$ 1.36	$ 2.29
Diluted earnings per common share (in dollars per share)										$ 1.34	$ 2.27