Business Combinations - Pro Forma Income Statements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total interest income	$ 45,233	$ 33,198	$ 133,521	$ 94,761
Total interest expense	8,504	3,760	22,037	9,955
Net interest income	36,729	29,438	111,484	84,806
Net interest income after provision for loan and lease losses	36,065	28,105	106,653	83,265
Total noninterest income	18,274	15,584	57,885	43,596
Total non-interest expense	33,592	28,184	105,458	83,339
Income before income taxes	20,747	15,505	59,080	43,522
Income tax expense	4,066	4,766	12,419	14,306
Net income attributable to Bryn Mawr Bank Corporation	$ 16,682	$ 10,739	$ 46,656	$ 29,216
Weighted-average basic shares outstanding (in shares)	20,270,706	17,023,046	20,237,757	16,987,499
Dilutive shares	167,670	230,936	206,318	254,728
Denominator for diluted earnings per share – adjusted weighted average shares outstanding	20,438,376	17,253,982	20,444,075	17,242,227
Basic earnings per share (in dollars per share)	$ 0.82	$ 0.63	$ 2.31	$ 1.72
Diluted earnings per share (in dollars per share)	$ 0.82	$ 0.62	$ 2.28	$ 1.69
Pro Forma
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Total interest income		$ 43,412		$ 126,976
Total interest expense		5,480		15,013
Net interest income		37,932		111,963
Provision for loan and lease losses		1,492		2,054
Net interest income after provision for loan and lease losses		36,440		109,909
Total noninterest income		16,015		45,481
Total non-interest expense		33,364		99,699
Income before income taxes		19,091		55,691
Income tax expense		5,843		18,306
Net income attributable to Bryn Mawr Bank Corporation		$ 13,248		$ 37,385
Weighted-average basic shares outstanding (in shares)		20,121,800		20,086,253
Dilutive shares		261,935		284,294
Denominator for diluted earnings per share – adjusted weighted average shares outstanding		20,383,735		20,370,547
Basic earnings per share (in dollars per share)		$ 0.66		$ 1.86
Diluted earnings per share (in dollars per share)		$ 0.65		$ 1.84