Investment Securities (Maturity Schedule) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Available-for-sale Securities, Debt Maturities [Abstract]
Due in one year or less, amortized cost	$ 18,716
Due in one year or less, estimated fair value	18,852
Due after one year through five years, amortized cost	42,764
Due after one year through five years, estimated fair value	43,074
Due after five years through ten years, amortized cost	3,266
Due after five years through ten years, estimated fair value	3,249
Due after ten years, amortized cost	6,646
Due after ten years, estimated fair value	6,981
Total, amortized cost	71,392
Total, estimated fair value	72,156
Mortgage-backed securities, amortized cost	487,426
Mortgage-backed securities, estimated fair value	492,694
Total, amortized cost	558,818
Estimated fair value	$ 564,850	$ 431,306