Fair Value Measurements Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 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	$ 2,790,834	$ 2,497,537
Significant input, assumed market return to liquidity (years)	5 years
Other real estate owned (OREO)	$ 6,593	6,831
Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average annual constant prepayment rate	14.90%
Weighted average discount rate	9.50%
Fair Value, Recurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
AFS, at estimated fair value	$ 2,790,834
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	2,695,008
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
AFS, at estimated fair value	95,826
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	359,400	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	10,200	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	8,000	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	2,200	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	3,900	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	377	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)	6,593	6,831
Net MSRs at end of period		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	527	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	6,000	1,200
Other financial liabilities	4,200	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	368,200	144,200
Other financial liabilities	$ 180,600	$ 76,000