Schedule of Underlying Assets of Federal Home Loan Bank Advances (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Assets Underlying Federal Home Loan Bank Advances [Line Items]
Assets pledged as collateral for Federal Home Loan Bank advances	$ 2,084,590	$ 4,287,485
Federal Home Loan Bank stock	85,175	167,856
Federal Home Loan Bank of Des Moines [Member]
Schedule of Assets Underlying Federal Home Loan Bank Advances [Line Items]
Federal Home Loan Bank stock	85,176	167,856
Available-for-sale Securities [Member]
Schedule of Assets Underlying Federal Home Loan Bank Advances [Line Items]
Assets pledged as collateral for Federal Home Loan Bank advances	2,048,924	3,576,481
Commercial Real Estate Assets [Member]
Schedule of Assets Underlying Federal Home Loan Bank Advances [Line Items]
Assets pledged as collateral for Federal Home Loan Bank advances	33,626	708,989
Retained Interest [Member]
Schedule of Assets Underlying Federal Home Loan Bank Advances [Line Items]
Assets pledged as collateral for Federal Home Loan Bank advances	$ 2,040	$ 2,015

[Line Items] for Schedule, as of the most recent balance sheet date, of securities or other assets underlying Federal Home Loan Bank advances, including type of securities or assets and market value.

No definition available.

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- Definition

Amount of the collateral pledged in support of federal home loan bank advances outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

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- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 325
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6478792&loc=d3e63345-112809

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