Investment Securities (Maturity Schedule) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Available-for-sale Securities, Debt Maturities [Abstract]
Due in one year or less, amortized cost	$ 8,436
Due in one year or less, estimated fair value	8,407
Due after one year through five years, amortized cost	33,381
Due after one year through five years, estimated fair value	33,459
Due after five years through ten years, amortized cost	4,749
Due after five years through ten years, estimated fair value	4,653
Due after ten years, amortized cost	6,864
Due after ten years, estimated fair value	7,096
Total, amortized cost	53,430
Total, estimated fair value	53,615
Mortgage-backed securities, amortized cost	420,008
Mortgage-backed securities, estimated fair value	423,521
Total, amortized cost	473,438
Total, estimated fair value	$ 477,136	$ 431,306