Investment Securities (Maturity Schedule) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Available-for-sale Securities, Debt Maturities [Abstract]
Due in one year or less, amortized cost	$ 16,486
Due in one year or less, estimated fair value	16,539
Due after one year through five years, amortized cost	10,445
Due after one year through five years, estimated fair value	10,551
Due after ten years, amortized cost	1,753
Due after ten years, estimated fair value	2,640
Total, amortized cost	28,684
Total, estimated fair value	29,730
Mortgage-backed securities, amortized cost	427,626
Mortgage-backed securities, estimated fair value	409,982
Total, amortized cost	456,310
Estimated fair value	439,712	564,850	[1]
Held-to-maturity Securities, Debt Maturities [Abstract]
Mortgage-backed securities, amortized cost	153,684
Mortgage-backed securities, estimated fair value	146,474
Total, amortized cost	153,684
Estimated fair value	$ 146,474

[1] Derived from audited consolidated financial statements