Fair Value Measurements (Details) (Recurring basis, USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value of Financial Instruments
Total securities available-for-sale	$ 428,374	$ 336,300
Residential mortgage-backed securities
Fair Value of Financial Instruments
Percentage of debt securities comprising available-for-sale portfolio	77.00%	71.00%
Available-for-sale residential mortgage-backed securities portfolio which are GSE securities (as a percent)	97.00%	95.00%
GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	299,203	204,827
Residential mortgage-backed securities portfolio which are Fixed-rate REMICs and CMOs	93.00%	90.00%
Non-GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	10,084	11,219
GSE pass-through certificates
Fair Value of Financial Instruments
Total securities available-for-sale	20,491	21,375
Obligations of GSEs
Fair Value of Financial Instruments
Total securities available-for-sale	98,595	98,879
Percentage of debt securities comprising available-for-sale portfolio	23.00%	29.00%
Fannie Mae stock
Fair Value of Financial Instruments
Total securities available-for-sale	1
Level 2
Fair Value of Financial Instruments
Total securities available-for-sale	428,373	336,300
Level 2 \| GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	299,203	204,827
Level 2 \| Non-GSE issuance REMICs and CMOs
Fair Value of Financial Instruments
Total securities available-for-sale	10,084	11,219
Level 2 \| GSE pass-through certificates
Fair Value of Financial Instruments
Total securities available-for-sale	20,491	21,375
Level 2 \| Obligations of GSEs
Fair Value of Financial Instruments
Total securities available-for-sale	98,595	98,879
Level 1
Fair Value of Financial Instruments
Total securities available-for-sale	(1)
Level 1 \| Fannie Mae stock
Fair Value of Financial Instruments
Total securities available-for-sale	$ (1)

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References+ Details