Accumulated Other Comprehensive (Loss) Income - Amounts Reclassified From Each Component of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other operating expenses	$ 4,668	$ 4,071	$ 12,970	$ 11,353
Other operating income	3,171	1,405	10,543	3,779
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
Amount Reclassified from Accumulated Other Comprehensive Loss | Net Change in Unrealized Gains on Available-for- Sale Investment Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Realization of gain on sale of investment securities available for sale	0	(72)	7	73
Other operating income	0	0	417	0
Income before income taxes	0	(72)	424	73
Income tax expense	0	(25)	89	27
Net income attributable to Bryn Mawr Bank Corporation	0	(47)	335	46
Amount Reclassified from Accumulated Other Comprehensive Loss | Net Change in Unfunded Pension Liability
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other operating expenses	25	24	75	71
Income tax expense	5	8	15	25
Net income attributable to Bryn Mawr Bank Corporation	$ 20	$ 16	$ 60	$ 46