Investment Securities (Maturities of Debt Securities) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Investment Securities Available-for-Sale:
Due in one year or less, Amortized Cost	$ 159,350
Due after one year through five years, Amortized Cost	371,009
Due after five years through ten years, Amortized Cost	78,876
Due after ten years, Amortized Cost	4,120
Preferred stock, Amortized Cost	1,389
Total Available-for-sale Securities, Debt Maturities, Amortized Cost	614,744
Due in one year or less , Fair Value	159,511
Due after one year through five years, Fair Value	371,673
Due after five years through ten years, Fair Value	79,101
Due after ten years, Fair Value	4,034
Preferred stock, Fair Value	1,656
Total Available-for-sale securities, Debt maturities, Fair Value	615,975
Investment Securities Held-to-Maturity:
Due in one year or less, Amortized Cost	34,176
Due after one year through five years, Amortized Cost	132,011
Due after five years through ten years, Amortized Cost	88,674
Due after ten years, Amortized Cost	53,269
Total Held-to-maturity securities, Debt maturities, Amortized Cost	308,130	273,905	274,715
Due in one year or less , Fair Value	34,260
Due after one year through five years, Fair Value	133,164
Due after five years through ten years, Fair Value	89,653
Due after ten years, Fair Value	46,884
Total Held-to-maturity securities, Debt maturities, Fair Value	$ 303,961	$ 268,271	$ 271,397