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, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating expense:
Interest	$ 14,245	$ 13,802	$ 13,125	$ 12,388	$ 12,175	$ 11,084	$ 8,162	$ 7,082	$ 53,560	$ 38,504	$ 24,301
Income tax benefit	(7,415)	(8,415)	(6,400)	(7,682)	(7,289)	(3,940)	(5,517)	(3,429)	(29,912)	(20,174)	(17,604)
Net income	17,786	15,289	11,556	13,952					58,583	43,214	32,694
Preferred stock dividend	1,006	980	507	0					2,493	0	0
Net income available to common shareholders	$ 16,780	$ 14,309	$ 11,049	$ 13,952	$ 13,178	$ 11,662	$ 10,233	$ 8,136	56,090	43,214	32,694
Comprehensive income									50,721	51,210	23,512
The Customer Bancorp
Operating income:
Other									18,545	90	758
Total operating income									18,545	90	758
Operating expense:
Interest									5,854	5,251	1,923
Other									4,604	5,611	3,395
Total operating expense									10,458	10,862	5,318
Income (loss) before taxes and undistributed income of subsidiaries									8,087	(10,772)	(4,560)
Income tax benefit									3,516	3,797	1,596
Income (loss) before undistributed income of subsidiaries									11,603	(6,975)	(2,964)
Equity in undistributed earnings of subsidiaries									46,980	50,189	35,658
Net income									58,583	43,214	32,694
Preferred stock dividend									2,493	0	0
Net income available to common shareholders									56,090	43,214	32,694
Comprehensive income									$ 50,721	$ 51,210	$ 23,512