Fair Value Measurements Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Equity securities, value test coverage	80.00%
Fair value price difference threshold	5.00%
Estimated Fair Value	$ 2,534,701
Other real estate owned (OREO)	$ 12,815	$ 11,099
Assumed market return to liquidity	5 years
Equity Securities Financial Institution
Available-for-sale securities, equity securities	$ 23,500	20,600
Equity Securities, Miscellaneous
Available-for-sale securities, equity securities	1,003	900
Corporate debt securities
Estimated Fair Value	109,409	96,955
Single-issuer trust preferred securities
Estimated Fair Value	39,829	39,106
Pooled trust preferred securities
Estimated Fair Value	422	706
Level 3 | Other Assets
Other real estate owned (OREO)	12,800	11,100
Net MSRs at end of year	37,500	40,900
Fair Value, Measurements, Recurring
Other financial assets	61,592	50,594
Other financial liabilities	58,766	48,924
Fair Value, Measurements, Recurring | Single-issuer trust preferred securities
Estimated Fair Value	39,800	39,100
Fair Value, Measurements, Recurring | Level 1
Other financial assets	17,111	16,129
Other financial liabilities	17,032	15,914
Fair Value, Measurements, Recurring | Level 1 | Equity Securities Financial Institution
Available-for-sale securities, equity securities	23,500	20,600
Fair Value, Measurements, Recurring | Level 1 | Equity Securities, Miscellaneous
Available-for-sale securities, equity securities	1,000	900
Fair Value, Measurements, Recurring | Level 2
Other financial assets	44,481	34,465
Other financial liabilities	41,734	33,010
Fair Value, Measurements, Recurring | Level 2 | Financial Institutions Subordinated Debt
Estimated Fair Value	65,200	53,100
Fair Value, Measurements, Recurring | Level 2 | Single-issuer trust preferred securities
Estimated Fair Value	37,300	36,500
Fair Value, Measurements, Recurring | Level 2 | Other Corporate Debt
Estimated Fair Value	4,000	4,000
Fair Value, Measurements, Recurring | Level 3
Other financial assets	0	0
Other financial liabilities	0	0
Fair Value, Measurements, Recurring | Level 3 | Single-issuer trust preferred securities
Estimated Fair Value	2,500	2,600
Fair Value, Measurements, Recurring | Level 3 | Pooled trust preferred securities
Estimated Fair Value	$ 422	700
Minimum
Assumptions used to estimate fair value, prepayment speed	12.60%
Assumptions used to estimate fair value, discount rate	10.10%
Trust for Benefit of Employees | Fair Value, Measurements, Recurring | Level 1
Other financial assets	$ 16,400	15,600
Foreign Exchange Contract | Fair Value, Measurements, Recurring | Level 1
Other financial assets	745	500
Forward Commitments | Fair Value, Measurements, Recurring | Level 2
Other financial assets	3,100	1,500
Other financial liabilities	339	0
Interest Rate Swap | Fair Value, Measurements, Recurring | Level 2
Other financial assets	41,400	33,000
Other financial liabilities	41,400	33,000
Foreign Exchange Contract | Fair Value, Measurements, Recurring | Level 1
Other financial liabilities	668	300
Trust for Benefit of Employees | Fair Value, Measurements, Recurring | Level 1
Other financial liabilities	$ 16,400	$ 15,600
Short Term Financial Instruments
Short term borrowings, reprice period	90