Fair Value Measurements Narrative (Details) - USD ($) shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Securities valued by the pricing service	95.00%
Researched securities to reconcile the difference	5.00%
AFS, at estimated fair value	$ 2,644,299	$ 2,497,537
Significant input, assumed market return to liquidity (years)	5 years
Other real estate owned (OREO)	$ 5,418	6,831
Common Class B [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investment owned, balance (in shares)	133
Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average annual constant prepayment rate	17.50%
Weighted average discount rate	9.50%
Fair Value, Recurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
AFS, at estimated fair value	$ 2,644,299
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
AFS, at estimated fair value	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
AFS, at estimated fair value	2,543,440
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
AFS, at estimated fair value	100,859
Fair Value, Recurring [Member] | Financial Institutions Subordinated Debt [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
AFS, at estimated fair value	321,000	362,300
Fair Value, Recurring [Member] | Single-issuer Trust Preferred Securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
AFS, at estimated fair value	0	11,200
Fair Value, Recurring [Member] | Single-issuer Trust Preferred Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
AFS, at estimated fair value	0	8,800
Fair Value, Recurring [Member] | Single-issuer Trust Preferred Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
AFS, at estimated fair value	0	2,400
Fair Value, Recurring [Member] | Other Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
AFS, at estimated fair value	4,400	3,900
Fair Value, Recurring [Member] | Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other financial liabilities	168	199
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned (OREO)	5,418	6,831
Net MSRs at end of period	30,992	45,193
Foreign Exchange Contract [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other financial assets	216	230
Forward Commitments [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other financial assets	10,600	1,200
Other financial liabilities	2,100	424
Interest Rate Swap [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other financial assets	390,700	144,200
Other financial liabilities	$ 188,500	$ 76,000