Accumulated Other Comprehensive (Loss) Income - Amounts Reclassified From Each Component of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other operating expenses	$ 4,985	$ 3,900	$ 8,302	$ 7,282
Other operating income	3,034	1,207	7,372	2,374
Income before income taxes	18,418	14,338	38,333	28,017
Income tax expense	3,723	4,905	8,353	9,540
Net income attributable to Bryn Mawr Bank Corporation	14,688	9,433	29,974	18,477
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			7	1
Other operating income			417	0
Income before income taxes			424	1
Income tax expense			89	0
Net income attributable to Bryn Mawr Bank Corporation			335	1
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	50	47
Income tax expense	5	8	10	16
Net income attributable to Bryn Mawr Bank Corporation	$ 20	$ 16	$ 40	$ 31