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Trading Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Schedule of Trading Securities [Line Items]
Trading securities	$ 1,613,400	$ 462,676	$ 614,117
Trading Securities, Net Unrealized Gain (Loss)	(3,733)	(448)	798
U.S. government agency residential mortgage-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	1,378,450	392,673	516,760
Trading Securities, Net Unrealized Gain (Loss)	(3,498)	(517)	723
Municipal and other tax-exempt securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	41,345	13,559	56,148
Trading Securities, Net Unrealized Gain (Loss)	(161)	83	153
U.S. government agency debentures [Member]
Schedule of Trading Securities [Line Items]
Trading securities	80,692	21,196	30,162
Trading Securities, Net Unrealized Gain (Loss)	21	8	(101)
Asset-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	72,309	23,885	0
Trading Securities, Net Unrealized Gain (Loss)	(100)	(26)	0
Other debt securities [Member]
Schedule of Trading Securities [Line Items]
Trading securities	40,604	11,363	11,047
Trading Securities, Net Unrealized Gain (Loss)	$ 5	$ 4	$ 23

X

- Definition

Represents the unrealized holding gain or loss included in the fair value of trading securities as of the balance sheet date.

+ References

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- Definition

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+ References

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

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