Condensed Financial Statements of Parent Company - Summary of Condensed Balance Sheets of Parent Company (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
ASSETS
Cash in subsidiary bank	$ 371,023	$ 233,068	$ 186,016	$ 73,570
LIABILITIES AND SHAREHOLDERS’ EQUITY
Other borrowings	88,250	63,250
Shareholders’ equity	443,145	386,623	269,475	147,748
Total liabilities and shareholders’ equity	6,825,370	4,153,173
The Customer Bancorp
ASSETS
Cash in subsidiary bank	16,465	13,254	44,679	4,999
Investment securities available for sale, at fair value	5	5
Investments in and receivables due from subsidiaries	509,465	432,064
Other assets	6,678	5,044
Total assets	532,613	450,367
LIABILITIES AND SHAREHOLDERS’ EQUITY
Other liabilities	1,218	494
Total liabilities	89,468	63,744
Shareholders’ equity	443,145	386,623
Total liabilities and shareholders’ equity	$ 532,613	$ 450,367