Fair Value Measurements Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities valued by the pricing service	80.00%	80.00%
Researched securities to reconcile the difference	5.00%	5.00%
Corporate debt securities	$ 2,467,244	$ 2,467,244
Significant input, assumed market return to liquidity (years)	5 years
Other real estate owned (OREO)	$ 11,432	11,432		$ 12,815
Transfer of student loans to loans held for sale		28,990	$ 0
Student Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfer of student loans to loans held for sale		$ 28,900
Loss on sale of loans receivable	440
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average annual constant prepayment rate		11.80%
Weighted average discount rate		9.50%
Equity Securities Financial Institution [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, equity securities	20,500	$ 20,500		23,500
Other Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, equity securities	1,000	1,000		1,000
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate debt securities	88,992	88,992		109,409
Single-issuer Trust Preferred Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate debt securities	42,478	42,478		39,829
Pooled Trust Preferred Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate debt securities	422	422		422
Fair Value, Measurements, Recurring [Member] | Single-issuer Trust Preferred Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate debt securities	42,500	42,500		39,800
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Trust for Benefit of Employees [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other financial assets	17,800	17,800		16,400
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other financial assets	716	716		745
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Trust for Benefit of Employees [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other financial liabilities	17,800	17,800		16,400
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other financial liabilities	626	626		668
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities Financial Institution [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, equity securities	20,500	20,500		23,500
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, equity securities	1,000	1,000		1,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other financial assets	1,400	1,400		3,100
Other financial liabilities	233	233		339
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other financial assets	48,300	48,300		41,400
Other financial liabilities	43,100	43,100		41,400
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Financial Institutions Subordinated Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate debt securities	42,100	42,100		65,200
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Single-issuer Trust Preferred Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate debt securities	39,700	39,700		37,300
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Corporate Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate debt securities	4,000	4,000		4,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Single-issuer Trust Preferred Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate debt securities	2,800	2,800		2,500
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Pooled Trust Preferred Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate debt securities	422	422		422
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned (OREO)	11,400	11,400		12,800
Other financial assets (MSRs)	$ 38,200	$ 38,200		$ 37,500