Investment Securities (Maturities of Debt Securities) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Investment Securities Available-for-Sale:
Due in one year or less, Amortized Cost	$ 153,539
Due after one year through five years, Amortized Cost	349,258
Due after five years through ten years, Amortized Cost	68,701
Due after ten years, Amortized Cost	3,853
Preferred stock, Amortized Cost	1,389
Total Available-for-sale Securities, Debt Maturities, Amortized Cost	576,740
Due in one year or less , Fair Value	153,302
Due after one year through five years, Fair Value	348,952
Due after five years through ten years, Fair Value	68,537
Due after ten years, Fair Value	3,778
Preferred stock, Fair Value	1,642
Total Available-for-sale securities, Debt maturities, Fair Value	576,211
Investment Securities Held-to-Maturity:
Due in one year or less, Amortized Cost	34,833
Due after one year through five years, Amortized Cost	135,150
Due after five years through ten years, Amortized Cost	95,222
Due after ten years, Amortized Cost	53,357
Total Held-to-maturity securities, Debt maturities, Amortized Cost	318,562	273,905	282,579
Due in one year or less , Fair Value	34,898
Due after one year through five years, Fair Value	136,359
Due after five years through ten years, Fair Value	95,839
Due after ten years, Fair Value	47,179
Total Held-to-maturity securities, Debt maturities, Fair Value	$ 314,275	$ 268,271	$ 275,866