Securities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Securities
Available-for-sale, amortized cost	$ 349,052	$ 330,481
Available-for-sale, Gross Unrealized Gains	2,380	6,510
Available-for-sale, Gross Unrealized Losses	(8,841)	(691)
Total available-for-sale securities	342,591	336,300
Held-to-maturity, amortized cost	1,892,883	1,700,141
Held-to-maturity, Gross Unrealized Gains	17,922	27,905
Held-to-maturity, Gross Unrealized Losses	(28,134)	(2,956)
Held-to-maturity, estimated fair value	1,882,671	1,725,090
Residential mortgage-backed securities
Securities
Available-for-sale, amortized cost	250,364	231,796
Available-for-sale, Gross Unrealized Gains	2,380	6,296
Available-for-sale, Gross Unrealized Losses	(3,643)	(671)
Total available-for-sale securities	249,101	237,421
Held-to-maturity, amortized cost	1,811,337	1,699,485
Held-to-maturity, Gross Unrealized Gains	17,922	27,905
Held-to-maturity, Gross Unrealized Losses	(24,130)	(2,956)
Held-to-maturity, estimated fair value	1,805,129	1,724,434
GSE issuance REMICs and CMOs
Securities
Available-for-sale, amortized cost	222,623	200,152
Available-for-sale, Gross Unrealized Gains	1,440	5,258
Available-for-sale, Gross Unrealized Losses	(3,605)	(583)
Total available-for-sale securities	220,458	204,827
Held-to-maturity, amortized cost	1,611,169	1,693,437
Held-to-maturity, Gross Unrealized Gains	17,832	27,787
Held-to-maturity, Gross Unrealized Losses	(16,910)	(2,955)
Held-to-maturity, estimated fair value	1,612,091	1,718,269
Non-GSE issuance REMICs and CMOs
Securities
Available-for-sale, amortized cost	9,175	11,296
Available-for-sale, Gross Unrealized Gains	3	9
Available-for-sale, Gross Unrealized Losses	(36)	(86)
Total available-for-sale securities	9,142	11,219
Held-to-maturity, amortized cost	4,648	5,791
Held-to-maturity, Gross Unrealized Gains	85	112
Held-to-maturity, estimated fair value	4,733	5,903
GSE pass-through certificates
Securities
Available-for-sale, amortized cost	18,566	20,348
Available-for-sale, Gross Unrealized Gains	937	1,029
Available-for-sale, Gross Unrealized Losses	(2)	(2)
Total available-for-sale securities	19,501	21,375
Held-to-maturity, amortized cost	195,520	257
Held-to-maturity, Gross Unrealized Gains	5	6
Held-to-maturity, Gross Unrealized Losses	(7,220)	(1)
Held-to-maturity, estimated fair value	188,305	262
Obligations of GSEs
Securities
Available-for-sale, amortized cost	98,673	98,670
Available-for-sale, Gross Unrealized Gains		214
Available-for-sale, Gross Unrealized Losses	(5,184)	(5)
Total available-for-sale securities	93,489	98,879
Held-to-maturity, amortized cost	80,924
Held-to-maturity, Gross Unrealized Losses	(4,004)
Held-to-maturity, estimated fair value	76,920
Fannie Mae stock
Securities
Available-for-sale, amortized cost	15	15
Available-for-sale, Gross Unrealized Losses	(14)	(15)
Total available-for-sale securities	1
Other
Securities
Held-to-maturity, amortized cost	622	656
Held-to-maturity, estimated fair value	$ 622	$ 656

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details

- Definition

For an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity. The held-to-maturity category is for those securities that the entity has the positive intent and ability to hold until maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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+ Details

- Definition

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.

+ References+ Details

- Definition

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.

+ References+ Details

- 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.

+ References+ Details