Fair Value Measurements (Schedule of Carrying Amounts and Estimated Fair Value of Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Investment securities:
Available-for-sale	$ 615,975	$ 684,570	$ 734,052
Held-to-maturity	303,961	268,271	271,397
Carrying Amount [Member]
Investment securities:
Nonmarketable equity securities	25,572	25,572	25,572
Carrying Amount [Member] | Level 1[Member]
Assets:
Cash and cash equivalents	140,294	310,788	206,957
Carrying Amount [Member] | Level 2 [Member]
Investment securities:
Available-for-sale	615,975	684,570	734,052
Held-to-maturity	297,630	263,405	264,215
Loans Held-for-sale	6,329	5,219	9,180
Interest receivable	15,827	15,748	15,844
Liabilities:
Deposits without defined maturities	3,814,013	3,790,454	3,434,266
Interest payable	735	868	1,085
Short-term borrowings	305,422	327,428	346,995
Carrying Amount [Member] | Level 3 [Member]
Investment securities:
Held-to-maturity	10,500	10,500	10,500
Net loans	4,821,011	4,568,549	4,253,687
Liabilities:
Time deposits	1,278,900	1,331,931	1,379,919
Fair Value [Member]
Investment securities:
Nonmarketable equity securities	25,572	25,572	25,572
Fair Value [Member] | Level 1[Member]
Assets:
Cash and cash equivalents	140,294	310,788	206,957
Fair Value [Member] | Level 2 [Member]
Investment securities:
Available-for-sale	615,975	684,570	734,052
Held-to-maturity	297,186	262,021	265,147
Loans Held-for-sale	6,329	5,219	9,180
Interest receivable	15,827	15,748	15,844
Liabilities:
Deposits without defined maturities	3,814,013	3,790,454	3,434,266
Interest payable	735	868	1,085
Short-term borrowings	305,422	327,428	346,995
Fair Value [Member] | Level 3 [Member]
Investment securities:
Held-to-maturity	6,775	6,250	6,250
Net loans	4,826,672	4,575,532	4,260,726
Liabilities:
Time deposits	$ 1,285,992	$ 1,340,746	$ 1,390,381