Components of Carrying Value of the Company's Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investments Debt And Equity Securities [Abstract]
Principal balance	$ 13,935,533	$ 16,864,583
Unamortized premium	381,851	490,187
Unamortized discount	(2,263)
Gross unrealized gains	143,490	267,771
Gross unrealized losses	(46,994)	(35,531)
Carrying value/estimated fair value	$ 14,411,617	$ 17,587,010

Available for sale unamortized discount.

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Available for sale unamortized premium.

+ References

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- Definition

The total mortgage backed securities and CRT securities owned by the entity for the period at fair value.

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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Includes other investments and securities that are not at fair value as of the balance sheet date and those that are not accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph a
-Subparagraph 1(g)
-Article 7

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