Condensed Financial Statements of Parent Company - Summary of Condensed Statements of Cash Flows of Parent Company (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Operating Activities:
Net income	$ 27,526	$ 27,066	$ 9,296	$ 15,440	$ 17,862	$ 6,029	$ 23,663	$ 24,142	$ 79,327	$ 71,695	$ 78,837
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
(Increase) decrease in other assets									(84,141)	(34,614)	(32,256)
Increase (decrease) in other liabilities									15,002	9,881	(16,687)
Net Cash Provided by (Used in) Operating Activities									78,280	97,474	62,193
Cash Flows from Investing Activities
Net Cash Used in Investing Activities									(1,444,435)	(104,098)	(565,125)
Cash Flows from Financing Activities
Proceeds from issuance of common stock									2,150	3,585	2,716
Proceeds from issuance of subordinated long-term debt									72,030	0	0
Proceed from issuance of other long-term borrowings									24,477	0	98,564
Repayments of other borrowings									(25,000)	(63,250)	0
Exercise and redemption of warrants									0	112	1,059
Purchase of treasury stock									(571)	(12,976)	0
Payments of employee taxes withheld from share-based awards									(1,732)	(880)	(14,761)
Preferred stock dividends paid									(14,459)	(14,459)	(14,459)
Net Cash Provided by (Used in) Financing Activities									1,516,525	(77,564)	384,546
Net Increase (Decrease) in Cash and Cash Equivalents									150,370	(84,188)	(118,386)
Cash and Cash Equivalents – Beginning				62,135				146,323	62,135	146,323	264,709
Cash and Cash Equivalents – Ending	212,505				62,135				212,505	62,135	146,323
Customers Bancorp
Cash Flows from Operating Activities:
Net income									79,327	71,695	78,837
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Equity in undistributed earnings of subsidiaries, net of dividends received from Bank									(14,105)	(33,838)	(46,743)
(Increase) decrease in other assets									(3,166)	(256)	7,624
Increase (decrease) in other liabilities									1,775	(251)	(1,322)
Net Cash Provided by (Used in) Operating Activities									63,831	37,350	38,396
Cash Flows from Investing Activities
Payments for investments in and advances to subsidiaries									(74,767)	(29)	(98,725)
Net Cash Used in Investing Activities									(74,767)	(29)	(98,725)
Cash Flows from Financing Activities
Proceeds from issuance of common stock									2,150	3,585	2,716
Proceeds from issuance of subordinated long-term debt									72,030	0	0
Proceed from issuance of other long-term borrowings									24,477	0	98,564
Repayments of other borrowings									(25,000)	(63,250)	0
Exercise and redemption of warrants									0	112	1,059
Purchase of treasury stock									(571)	(12,976)	0
Payments of employee taxes withheld from share-based awards									(1,732)	(880)	(14,761)
Preferred stock dividends paid									(14,459)	(14,459)	(14,459)
Net Cash Provided by (Used in) Financing Activities									56,895	(87,868)	73,119
Net Increase (Decrease) in Cash and Cash Equivalents									45,959	(50,547)	12,790
Cash and Cash Equivalents – Beginning				$ 16,684				$ 67,231	16,684	67,231	54,441
Cash and Cash Equivalents – Ending	$ 62,643				$ 16,684				$ 62,643	$ 16,684	$ 67,231