Accrued Interest Payable

No definition available.

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- Definition

Collateral ratio.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Repurchase obligation, maturity.

+ References

No definition available.

+ Details

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- Definition

Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

+ 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

+ Details

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Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

The calculated average balance outstanding for the year for all Federal Home Loan Bank advances as of the Balance Sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(3)(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The calculated weighted average interest rate for Federal Home Loan Bank advances for the period ended as of the Balance Sheet date.

+ References

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Maturity period on variable rate advances made and reported by Federal Home Loan Bank (FHLBank), in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Borrowings - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
Borrowings - Additional Information (Detail) - USD ($)	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2013
Repurchase Agreement Counterparty
Collateral ratio	110.00%	110.00%
Advances from Federal Home Loan Banks	$ 1,650,000,000	$ 1,650,000,000
Minimum
Repurchase Agreement Counterparty
Repurchase obligation maturity	1 month
Maximum
Repurchase Agreement Counterparty
Repurchase obligation maturity	12 months
FHLBI
Repurchase Agreement Counterparty
Advances from Federal Home Loan Banks	$ 1,650,000,000
Average outstanding borrowings from FHLBI	$ 1,650,000,000
FHLBI weighted average interest rate on advances	1.68%
Weighted average maturity (in years)	6 years 1 month 24 days
Exchangeable Senior Notes
Repurchase Agreement Counterparty
Debt principal amount			$ 400,000,000
Accrued interest payable		$ 2,100,000