Number of interest rate derivative instruments added.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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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.

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The amount of net gains or losses on interest rate cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income upon the hedged transaction affecting earnings.

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The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

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Derivative Insturments - Fair value of Derivative Instruments (Detail) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018 USD ($) item	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Derivative [Line Items]
Fair value of derivative assets	$ 69,639	$ 69,639	$ 27,793
Fair value of derivative liabilities	652	652	1,335
AOCI relating to interest rate swaps		13,600
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months	4,100	4,100
Interest rate swaps
Derivative [Line Items]
Fair value of derivative assets	67,735	67,735	27,793
Fair value of derivative liabilities	$ 652	$ 652	51
Interest rate swap agreements
Derivative [Line Items]
Derivative contract, weighted average maturity (in months)		48 months
Number of new swap agreements \| item	4
TBA Agency MBS
Derivative [Line Items]
Fair value of derivative assets	$ 1,904	$ 1,904
Fair value of derivative liabilities			$ 1,284
Eurodollar Future
Derivative [Line Items]
Derivative contract, weighted average maturity (in months)		3 months
Minimum \| Interest rate swap agreements
Derivative [Line Items]
Fixed interest rate	1.001%	1.001%
Minimum \| TBA Agency MBS
Derivative [Line Items]
Fixed interest rate	3.50%	3.50%
Maximum \| Interest rate swap agreements
Derivative [Line Items]
Fixed interest rate	3.0295%	3.0295%
Maximum \| TBA Agency MBS
Derivative [Line Items]
Fixed interest rate	4.00%	4.00%