Fair Value Accounting (Fair Value Inputs, Assets, Quantitative Information) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale, at fair value	$ 6,937,240	$ 6,778,670
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale, at fair value	6,937,240	6,778,670
Investment Securities Available for Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	1,562	2,105	$ 1,981	$ 1,785
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale, at fair value	1,562	2,105
Fair Value, Measurements, Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale, at fair value	6,937,240	6,778,670
Fair Value, Measurements, Recurring Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available for sale, at fair value	1,562	$ 2,105
Fair Value, Measurements, Recurring Basis | Level 3 | Investment Securities Available for Sale | Discounted cash flow analysis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	$ 1,562
Discount rate	7.01%
Forecasted average Prime reset rate	3.56%
Fair Value, Measurements, Recurring Basis | Level 3 | Private equity investments | Individual analysis of each investee company
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	$ 3,255
Fair Value, Measurements, Recurring Basis | Level 3 | GGL/SBA loans servicing asset | Discounted cash flow analysis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	$ 3,149
Discount rate	12.16%
Prepayment speeds	16.10%
Fair Value, Measurements, Recurring Basis | Level 3 | Earnout liability | Option pricing methods and Monte Carlo simulation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	$ 11,016
Fair Value, Measurements, Recurring Basis | Level 3 | Visa derivative liability | Discounted cash flow analysis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	$ 2,050
Estimated timing of resolution of covered litigation and future cumulative deposits to the litigation escrow for settlement of the Covered Litigation	2 years
Fair Value, Measurements, Nonrecurring Basis | Level 3 | Other real estate | Third-party appraised value of real estate less estimated selling costs | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	0.00%
Estimated selling costs	0.00%
Fair Value, Measurements, Nonrecurring Basis | Level 3 | Other real estate | Third-party appraised value of real estate less estimated selling costs | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	1.00%
Estimated selling costs	10.00%
Fair Value, Measurements, Nonrecurring Basis | Level 3 | Other real estate | Third-party appraised value of real estate less estimated selling costs | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	1.00%
Estimated selling costs	7.00%
Fair Value, Measurements, Nonrecurring Basis | Level 3 | Other assets held for sale | Third-party appraised value less estimated selling costs or BOV | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	0.00%
Estimated selling costs	0.00%
Fair Value, Measurements, Nonrecurring Basis | Level 3 | Other assets held for sale | Third-party appraised value less estimated selling costs or BOV | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	76.00%
Estimated selling costs	10.00%
Fair Value, Measurements, Nonrecurring Basis | Level 3 | Other assets held for sale | Third-party appraised value less estimated selling costs or BOV | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	58.00%
Estimated selling costs	7.00%