Parent Company - Only Financial Statements - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating activities:
Net income attributable to Bryn Mawr Bank Corporation	$ 15,537	$ 13,164	$ 15,035	$ (11,163)	$ 16,384	$ 16,360	$ 15,785	$ 10,677	$ 32,573	$ 59,206	$ 63,792
Adjustments to reconcile net income to net cash provided by operating activities:
Net gain on sale of long-lived assets									(2,297)	0	0
Stock-based compensation									3,044	3,725	2,750
Other, net									786	(475)	532
Investing activities:
Proceeds from the sale of long-lived assets									3,166	0	0
Net cash used in investing activities									(99,853)	(543,380)	(220,218)
Financing activities:
Dividends paid									(21,356)	(20,685)	(19,289)
Cash payments to taxing authorities on employees' behalf from shares withheld from stock-based compensation									(633)	(625)	(1,639)
Proceeds from exercise of stock options									12	907	1,464
Repurchase of warrants from U.S. Treasury									0	0	(1,755)
Net cash provided by financing activities									70,959	455,474	129,415
Cash and cash equivalents at beginning of period				53,931					53,931
Cash and cash equivalents at end of period	96,313				53,931				96,313	53,931
Parent Company
Operating activities:
Net income attributable to Bryn Mawr Bank Corporation									32,573	59,206	63,792
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed income of subsidiaries									9,144	(23,048)	(32,779)
Net gain on sale of long-lived assets									(2,295)	0	0
Net amortization of investment premiums and discounts									95	98	98
Stock-based compensation									3,144	3,725	2,750
Other, net									126	225	2,860
Net cash provided by operating activities									42,787	40,206	36,721
Investing activities:
Net change in trading securities									0	0	40
Proceeds from the sale of long-lived assets									3,197	0	0
Net cash used in investing activities									3,197	0	40
Financing activities:
Dividends paid									(21,356)	(20,685)	(19,289)
Net (purchase of) proceeds from sale of treasury stock for deferred compensation plans									(153)	(172)
Net (purchase of) proceeds from sale of treasury stock for deferred compensation plans											2
Net purchase of treasury stock through publicly announced plans									(7,249)	(4,524)	(5,936)
Cash payments to taxing authorities on employees' behalf from shares withheld from stock-based compensation									(633)	(625)	(1,639)
Proceeds from exercise of stock options									12	907	1,464
Repurchase of warrants from U.S. Treasury									0	0	(1,755)
Net cash provided by financing activities									(29,379)	(25,099)	(27,153)
Change in cash and cash equivalents									16,605	15,107	9,608
Cash and cash equivalents at beginning of period				$ 93,250				$ 78,143	93,250	78,143	68,535
Cash and cash equivalents at end of period	$ 109,855				$ 93,250				$ 109,855	$ 93,250	$ 78,143