Fair Value Measurements Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Securities valued by the pricing service	95.00%	95.00%
Researched securities to reconcile the difference	5.00%	5.00%
Available for sale, at estimated fair value	$ 2,285,794	$ 2,285,794	$ 2,080,294
Significant input, assumed market return to liquidity (years)	5 years
Other real estate owned (OREO)	$ 7,241	$ 7,241	10,518
Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average annual constant prepayment rate		10.20%
Weighted average discount rate		9.50%
Fair Value, Measurements, Recurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale, at estimated fair value	2,285,794	$ 2,285,794
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale, at estimated fair value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale, at estimated fair value	2,180,059	2,180,059
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale, at estimated fair value	105,735	105,735
Fair Value, Measurements, Recurring [Member] | Financial Institutions Subordinated Debt [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale, at estimated fair value	175,200	175,200	86,100
Fair Value, Measurements, Recurring [Member] | Single-issuer Trust Preferred Securities [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale, at estimated fair value	18,300	18,300	18,600
Fair Value, Measurements, Recurring [Member] | Single-issuer Trust Preferred Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale, at estimated fair value	16,000	16,000	16,300
Fair Value, Measurements, Recurring [Member] | Single-issuer Trust Preferred Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale, at estimated fair value	2,400	2,400	2,400
Fair Value, Measurements, Recurring [Member] | Pooled Trust Preferred Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale, at estimated fair value	0	0	875
Fair Value, Measurements, Recurring [Member] | Other Corporate Debt [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale, at estimated fair value	3,900	3,900	3,900
Fair Value, Measurements, Recurring [Member] | Trust for Benefit of Employees [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other financial liabilities	20,800	20,800	18,400
Fair Value, Measurements, Recurring [Member] | Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other financial liabilities	286	286	381
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned (OREO)	7,241	7,241	10,518
Net MSRs at end of period	44,916	44,916	50,204
Foreign Exchange Contract [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other financial assets	331	331	392
Forward Commitments [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other financial assets	2,300	2,300	1,200
Other financial liabilities	1,700	1,700	1,100
Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other financial assets	138,000	138,000	61,400
Other financial liabilities	$ 76,200	$ 76,200	$ 47,100