Investment Securities Held-to-Maturity (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Unrealized gain (losses) on securities
Amortized Cost	$ 275,507	$ 179,368
Gross Unrealized Gains	6,499	5,471
Gross Unrealized Losses	82	17
Estimated Fair Value	281,924	184,822
U.S. Government Sponsored Enterprises [Member]
Unrealized gain (losses) on securities
Amortized Cost	17,747	26,979
Gross Unrealized Gains	19	36
Gross Unrealized Losses	8	2
Estimated Fair Value	17,758	27,013
U.S. Government Agency and Sponsored Enterprises Mortgage-Backed Securities [Member]
Unrealized gain (losses) on securities
Amortized Cost	257,760	152,389
Gross Unrealized Gains	6,480	5,435
Gross Unrealized Losses	74	15
Estimated Fair Value	$ 264,166	$ 157,809

This item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.

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As of the balance sheet date, the excess of fair value over carrying value (amortized cost) of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding gain.

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- Definition

As of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss.

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