Condensed Financial Statements of Parent Company - Summary of Condensed Balance Sheets of Parent Company (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
ASSETS
Cash in bank subsidiary	$ 693,354	$ 212,505
Other assets	389,706	298,052
Total assets	18,439,248	11,520,717	$ 9,833,425
LIABILITIES AND SHAREHOLDERS’ EQUITY
Other borrowings	124,037	123,630
Total liabilities	17,322,162	10,467,922
Shareholders' equity	1,117,086	1,052,795	$ 956,816	$ 920,964
Total liabilities and shareholders’ equity	18,439,248	11,520,717
Customers Bancorp
ASSETS
Cash in bank subsidiary	110,626	62,643
Other assets	970	6,583
Total assets	1,314,306	1,249,798
LIABILITIES AND SHAREHOLDERS’ EQUITY
Other borrowings	196,259	195,670
Other liabilities	961	1,333
Total liabilities	197,220	197,003
Shareholders' equity	1,117,086	1,052,795
Total liabilities and shareholders’ equity	1,314,306	1,249,798
Bank Subsidiaries
ASSETS
Investments in and receivables due from bank subsidiary	1,198,857	1,178,166
Non-Bank Subsidiaries
ASSETS
Investments in and receivables due from bank subsidiary	$ 3,853	$ 2,406