Securities (Amortized Cost and Fair Value of Securities by Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Securities Available-for-Sale: Amortized cost
Due in one year or less	$ 4,588
Due after one year through five years	12,427
Due after five years through ten years	52,458
Due after ten years	25,198
Total	617,785	571,058
Securities Available-for-Sale, Fair Value
Due in one year or less	4,640
Due after one year through five years	12,785
Due after five years through ten years	54,692
Due after ten years	27,165
Total	630,881	587,602
Securities Held-to-Maturity, Carrying Amount
Due in one year or less	0
Due after one year through five years	268
Due after five years through ten years	0
Due after ten years	0
Total	268	346
Securities Held-to-Maturity, Fair Value
Due in one year or less	0
Due after one year through five years	271
Due after five years through ten years	0
Due after ten years	0
Fair Value	271	351
Mortgage-backed Securities - Residential [Member]
Securities Available-for-Sale: Amortized cost
Available-for-Sale, amortized cost	522,430
Total	522,430	475,452
Securities Available-for-Sale, Fair Value
Available-for-Sale, Fair Value	530,827
Total	530,827	486,912
Equity Securities [Member]
Securities Available-for-Sale: Amortized cost
Available-for-Sale, amortized cost	684
Total	684	684
Securities Available-for-Sale, Fair Value
Available-for-Sale, Fair Value	772
Total	$ 772	$ 733