Accumulated Other Comprehensive (Loss) Income - Amounts Reclassified From Each Component of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other operating income	$ 2,847	$ 4,338
Income before income taxes	13,440	19,915
Income tax expense	2,764	4,630
Net income attributable to Bryn Mawr Bank Corporation	10,677	15,286
Other operating expenses	4,614	3,317
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	(7)
Other operating income	0	(417)
Income before income taxes	0	(424)
Income tax expense	0	89
Net income attributable to Bryn Mawr Bank Corporation	0	(335)
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]
Income tax expense	(2)	(5)
Net income attributable to Bryn Mawr Bank Corporation	9	20
Other operating expenses	$ 11	$ 25