Fair Value Measurements, Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	$ 3,085,441	$ 3,262,586
Fair Value, Inputs, Level 1
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	26,531	0
Fair Value, Inputs, Level 2
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	3,058,910	3,262,586
Fair Value, Inputs, Level 3
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	9,624	2,527
Liabilities, Fair Value Disclosure [Abstract]
Net Amounts Presented on the Consolidated Balance Sheets	2,046	710
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 | U.S. Treasury securities
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	26,531	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	1,661	1,646
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 | Total investment securities AFS
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	26,531	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | FFELP
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	327,189	263,693
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Other debt securities
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	3,000	3,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Total investment securities AFS
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	3,058,910	3,262,586
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Residential loans held for sale
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	129,158	136,280
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Interest rate-related instruments(a)
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	192,518	77,024
Liabilities, Fair Value Disclosure [Abstract]
Net Amounts Presented on the Consolidated Balance Sheets	25,680	13,073
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Foreign currency exchange forwards(a)
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	4,909	4,226
Liabilities, Fair Value Disclosure [Abstract]
Net Amounts Presented on the Consolidated Balance Sheets	4,836	4,048
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Commodity contracts(a)
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	12,486	20,528
Liabilities, Fair Value Disclosure [Abstract]
Net Amounts Presented on the Consolidated Balance Sheets	11,155	19,624
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 | Interest rate lock commitments to originate residential mortgage loans held for sale
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	9,624	2,527
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 | Forward commitments to sell residential mortgage loans
Liabilities, Fair Value Disclosure [Abstract]
Net Amounts Presented on the Consolidated Balance Sheets	2,046	710
FNMA / FHLMC | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | FNMA / FHLMC
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	1,461,241	132,660
FNMA / FHLMC | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Commercial mortgage-related securities
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	22,904	21,728
GNMA | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 | Commercial mortgage-related securities
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	524,756	1,310,207
U.S. Treasury securities
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	26,531
Agency securities
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	25,038
Agency securities | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	25,038	0
Obligations of state and political subdivisions (municipal securities)
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	450,662	546,160
Obligations of state and political subdivisions (municipal securities) | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	450,662	546,160
SBA
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	8,584
SBA | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2
Assets, Fair Value Disclosure [Abstract]
Investment securities available for sale	$ 8,584	$ 0