Consolidated Statements of Changes in Shareholders' Equity - Unaudited - USD ($) $ in Thousands		Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred Stock	Common Stock	Additional Paid in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Customers Bank Additional Paid in Capital
Beginning balance, preferred stock (shares) at Dec. 31, 2018				9,000,000
Beginning balance, common stock (shares) at Dec. 31, 2018					31,003,028
Beginning balance at Dec. 31, 2018		$ 956,816		$ 217,471	$ 32,252	$ 434,314	$ 316,651		$ (22,663)	$ (21,209)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		24,735					24,735
Other comprehensive income (loss)		12,670							12,670
Preferred stock dividends	[1]	(7,229)					(7,229)
Share-based compensation expense		4,425				4,425
Issuance of common stock under share-based compensation arrangements (shares)					230,154
Issuance of common stock under share-based compensation arrangements		559			$ 231	328
Repurchase of common shares (shares)					(31,159)
Repurchase of common shares		(571)								(571)
Ending balance, preferred stock (shares) at Jun. 30, 2019				9,000,000
Ending balance, common stock (shares) at Jun. 30, 2019					31,202,023
Ending balance at Jun. 30, 2019		$ 991,405		$ 217,471	$ 32,483	439,067	334,157		(9,993)	(21,780)
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201613Member
Beginning balance, preferred stock (shares) at Dec. 31, 2018				9,000,000
Beginning balance, common stock (shares) at Dec. 31, 2018					31,003,028
Beginning balance at Dec. 31, 2018		$ 956,816		$ 217,471	$ 32,252	434,314	316,651		(22,663)	(21,209)
Ending balance, preferred stock (shares) at Dec. 31, 2019		9,000,000		9,000,000
Ending balance, common stock (shares) at Dec. 31, 2019		31,336,791			31,336,791
Ending balance at Dec. 31, 2019		$ 1,052,795	$ 61,475	$ 217,471	$ 32,617	444,218	381,519	$ 61,475	(1,250)	(21,780)
Beginning balance, preferred stock (shares) at Mar. 31, 2019				9,000,000
Beginning balance, common stock (shares) at Mar. 31, 2019					31,131,247
Beginning balance at Mar. 31, 2019		978,373		$ 217,471	$ 32,412	436,713	328,476		(14,919)	(21,780)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		9,296					9,296
Other comprehensive income (loss)		4,926							4,926
Preferred stock dividends	[2]	(3,615)					(3,615)
Share-based compensation expense		2,315				2,315
Issuance of common stock under share-based compensation arrangements (shares)					70,776
Issuance of common stock under share-based compensation arrangements		110			$ 71	39
Ending balance, preferred stock (shares) at Jun. 30, 2019				9,000,000
Ending balance, common stock (shares) at Jun. 30, 2019					31,202,023
Ending balance at Jun. 30, 2019		$ 991,405		$ 217,471	$ 32,483	439,067	334,157		(9,993)	(21,780)
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201613Member
Beginning balance, preferred stock (shares) at Dec. 31, 2019		9,000,000		9,000,000
Beginning balance, common stock (shares) at Dec. 31, 2019		31,336,791			31,336,791
Beginning balance at Dec. 31, 2019		$ 1,052,795	$ 61,475	$ 217,471	$ 32,617	444,218	381,519	$ 61,475	(1,250)	(21,780)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		25,817					25,817
Other comprehensive income (loss)		(8,715)							(8,715)
Preferred stock dividends	[1]	(7,196)					(7,196)
Share-based compensation expense		6,827				6,827
Issuance of common stock under share-based compensation arrangements (shares)					173,496
Issuance of common stock under share-based compensation arrangements		$ (206)			$ 174	(380)
Ending balance, preferred stock (shares) at Jun. 30, 2020		9,000,000		9,000,000
Ending balance, common stock (shares) at Jun. 30, 2020		31,510,287			31,510,287
Ending balance at Jun. 30, 2020		$ 1,007,847		$ 217,471	$ 32,791	450,664	338,665		(9,965)	(21,780)	$ 450,665
Beginning balance, preferred stock (shares) at Mar. 31, 2020				9,000,000
Beginning balance, common stock (shares) at Mar. 31, 2020					31,470,026
Beginning balance at Mar. 31, 2020		964,636		$ 217,471	$ 32,751	446,840	319,529		(30,175)	(21,780)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		22,718					22,718
Other comprehensive income (loss)		20,210							20,210
Preferred stock dividends	[2]	(3,581)					(3,581)
Share-based compensation expense		3,599				3,599
Issuance of common stock under share-based compensation arrangements (shares)					40,261
Issuance of common stock under share-based compensation arrangements		$ 265			$ 40	225
Ending balance, preferred stock (shares) at Jun. 30, 2020		9,000,000		9,000,000
Ending balance, common stock (shares) at Jun. 30, 2020		31,510,287			31,510,287
Ending balance at Jun. 30, 2020		$ 1,007,847		$ 217,471	$ 32,791	$ 450,664	$ 338,665		$ (9,965)	$ (21,780)	$ 450,665

[1] Dividends per share of $0.8750, $0.81250, $0.806250, and $0.750 per share were declared on Series C, D, E, and F preferred stock for the six months ended June 30, 2020 and 2019, respectively.

[2] Dividends per share of $0.4375, $0.40625, $0.403125, and $0.375 per share were declared on Series C, D, E, and F preferred stock for the three months ended June 30, 2020 and 2019, respectively.