Regulatory Capital - Narrative (Details)	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Jan. 01, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Maximum buffer, percent of risk weighted assets for 2016	0.625%
Maximum buffer, percent of risk weighted assets for 2017	1.25%
Maximum buffer, percent of risk weighted assets for 2018	1.875%
Maximum buffer, percent of risk weighted assets for 2019 and thereafter	2.50%
Common equity Tier 1 (to risk-weighted assets), for capital adequacy purposes ratio	4.50%		4.50%
Tier 1 capital (to risk-weighted assets), for capital adequacy purposes ratio	6.00%		6.00%
Total capital (to risk-weighted assets), for capital adequacy purposes ratio	8.00%		8.00%
Capital conservation buffer, excess of minimum capital ratio				2.50%
Customers Bancorp, Inc.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common equity Tier 1 (to risk-weighted assets), for capital adequacy purposes ratio		7.00%
Tier 1 capital (to risk-weighted assets), for capital adequacy purposes ratio		8.50%
Total capital (to risk-weighted assets), for capital adequacy purposes ratio		10.50%