Fair Value Measurements Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 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	$ 2,315,541	$ 2,315,541	$ 2,080,294
Significant input, assumed market return to liquidity (years)	5 years
Other real estate owned (OREO)	$ 7,706	$ 7,706	10,518
Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted average annual constant prepayment rate		10.70%
Weighted average discount rate		10.00%
Fair Value, Measurements, Recurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available for sale, at estimated fair value	2,315,541	$ 2,315,541
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	2,209,873	2,209,873
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	105,668	105,668
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	336,000	336,000	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	18,500	18,500	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	16,100	16,100	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] \| Foreign Exchange Contract [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other financial liabilities	480	480	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)	7,706	7,706	10,518
Net MSRs at end of period	43,968	43,968	50,200
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	535	535	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	1,800	1,800	1,200
Other financial liabilities	287	287	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	193,600	193,600	61,400
Other financial liabilities	$ 104,700	$ 104,700	$ 47,100

Differences by security in excess of of threhold are researched to reconcile the difference.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Carrying amount as of the balance sheet date of other real estate and foreclosed assets. Other real estate may include real estate investments, real estate loans that qualify as investments in real estate, and premises that are no longer used in operations may also be included in real estate owned. Foreclosed assets include all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings.

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Fair value of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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