Fair Value Measurements (Schedule of Carrying Amounts and Estimated Fair Value of Financial Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Investment securities:
Available-for-sale	$ 458,552	$ 553,731	$ 685,706
Held-to-maturity	568,415	512,705	466,578
Carrying Amount [Member]
Investment securities:
Nonmarketable equity securities	47,775	36,907	36,142
Carrying Amount [Member] | Level 1[Member]
Assets:
Cash and cash equivalents	232,960	238,789	215,034
Investment securities:
Available-for-sale	5,810	5,765	8,294
Carrying Amount [Member] | Level 2 [Member]
Investment securities:
Available-for-sale	452,742	547,966	677,412
Held-to-maturity	552,328	509,471	469,337
Loans Held-for-sale	13,990	10,327	7,798
Interest receivable	23,111	21,953	21,668
Liabilities:
Deposits without defined maturities	5,904,618	5,809,355	5,547,764
Interest payable	1,389	1,578	1,557
Short-term borrowings	556,213	397,199	532,291
Long-term borrowings	354,320	206,394	106,469
Carrying Amount [Member] | Level 3 [Member]
Investment securities:
Held-to-maturity	500	500	500
Net loans	7,575,763	7,197,819	6,959,802
Liabilities:
Time deposits	1,560,028	1,647,412	1,745,215
Long-term borrowings	17,277	35,997	42,021
Fair Value [Member]
Investment securities:
Nonmarketable equity securities	47,775	36,907	36,142
Fair Value [Member] | Level 1[Member]
Assets:
Cash and cash equivalents	232,960	238,789	215,034
Investment securities:
Available-for-sale	5,810	5,765	8,294
Fair Value [Member] | Level 2 [Member]
Investment securities:
Available-for-sale	452,742	547,966	677,412
Held-to-maturity	568,130	512,405	466,278
Loans Held-for-sale	13,990	10,327	7,798
Interest receivable	23,111	21,953	21,668
Liabilities:
Deposits without defined maturities	5,904,618	5,809,355	5,547,764
Interest payable	1,389	1,578	1,557
Short-term borrowings	556,213	397,199	532,291
Long-term borrowings	359,043	206,394	106,469
Fair Value [Member] | Level 3 [Member]
Investment securities:
Held-to-maturity	285	300	300
Net loans	7,593,013	7,201,994	6,969,655
Liabilities:
Time deposits	1,563,446	1,647,412	1,745,215
Long-term borrowings	$ 17,228	$ 35,997	$ 42,021