Fair Value of Financial Instruments, Part 3 (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Financial assets [Abstract]
Cash and cash equivalents	$ 664,428	$ 718,156	$ 698,072	$ 671,448
Securities available for sale	654,502	601,037
Held to maturity securities	50,991	59,439
Net loans	3,414,401	3,279,167
Accrued interest receivable	10,872	10,262
Financial liabilities [Abstract]
Demand deposits	380,090	365,081
Interest bearing deposits	3,789,867	3,738,607
Short-term borrowings	179,204	191,226
Accrued interest payable	496	501
Level 1 [Member]
Financial assets [Abstract]
Cash and cash equivalents	664,428	718,156
Securities available for sale	35	35
Held to maturity securities	0	0
Net loans	0	0
Accrued interest receivable	25	80
Financial liabilities [Abstract]
Demand deposits	380,090	365,081
Interest bearing deposits	2,628,949	2,627,367
Short-term borrowings	0	0
Accrued interest payable	72	74
Level 2 [Member]
Financial assets [Abstract]
Cash and cash equivalents	0	0
Securities available for sale	654,467	601,002
Held to maturity securities	50,991	59,439
Net loans	0	0
Accrued interest receivable	2,695	2,370
Financial liabilities [Abstract]
Demand deposits	0	0
Interest bearing deposits	1,160,918	1,111,240
Short-term borrowings	179,204	191,226
Accrued interest payable	424	427
Level 3 [Member]
Financial assets [Abstract]
Cash and cash equivalents	0	0
Securities available for sale	0	0
Held to maturity securities	0	0
Net loans	3,414,401	3,279,167
Accrued interest receivable	8,152	7,812
Financial liabilities [Abstract]
Demand deposits	0	0
Interest bearing deposits	0	0
Short-term borrowings	0	0
Accrued interest payable	0	0
Carrying Value [Member]
Financial assets [Abstract]
Cash and cash equivalents	664,428	718,156
Securities available for sale	654,502	601,037
Held to maturity securities	48,030	56,465
Federal Reserve Bank and Federal Home Loan Bank stock	9,579	9,480
Net loans	3,343,681	3,248,542
Accrued interest receivable	10,872	10,262
Financial liabilities [Abstract]
Demand deposits	380,090	365,081
Interest bearing deposits	3,788,148	3,735,297
Short-term borrowings	179,204	191,226
Accrued interest payable	$ 496	$ 501