Condensed Financial Statements of Parent Company - Summary of Condensed Income Statements 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
Operating expense:
Interest	$ 46,402	$ 50,983	$ 47,271	$ 41,771	$ 41,779	$ 46,044	$ 40,317	$ 31,933	$ 186,429	$ 160,074	$ 105,507
Income tax benefit	(7,451)	(8,020)	(2,491)	(4,831)	(5,109)	(28)	(6,820)	(7,402)	(22,793)	(19,359)	(45,042)
Net income	27,526	27,066	9,296	15,440	17,862	6,029	23,663	24,142	79,327	71,695	78,837
Preferred stock dividends	3,615	3,615	3,615	3,615	3,615	3,615	3,615	3,615	14,459	14,459	14,459
Net income available to common shareholders	$ 23,911	$ 23,451	$ 5,681	$ 11,825	$ 14,247	$ 2,414	$ 20,048	$ 20,527	64,868	57,236	64,378
Comprehensive income									100,740
Customers Bancorp
Operating income:
Other, including dividends from bank subsidiary									70,000	45,422	38,200
Total operating income									70,000	45,422	38,200
Operating expense:
Interest									5,425	8,178	7,984
Other									744	1,722	1,742
Total operating expense									6,169	9,900	9,726
Income before taxes and undistributed income of subsidiaries									63,831	35,522	28,474
Income tax benefit									1,391	2,335	3,620
Income before undistributed income of subsidiaries									65,222	37,857	32,094
Equity in undistributed income of subsidiaries									14,105	33,838	46,743
Net income									79,327	71,695	78,837
Preferred stock dividends									14,459	14,459	14,459
Net income available to common shareholders									64,868	57,236	64,378
Comprehensive income									$ 100,740	$ 50,730	$ 83,370