Derivative Instruments - Fair value of Derivative Instruments (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)
Derivative [Line Items]
Fair value of derivative assets	$ 27,396	$ 46,207
Fair value of derivative liabilities	36,261	15,901
AOCI relating to interest rate swaps	10,500
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months	3,800
Interest rate swaps
Derivative [Line Items]
Fair value of derivative assets	22,974	40,192
Fair value of derivative liabilities	36,261	15,901
Interest rate swap agreements
Derivative [Line Items]
Fair value of derivative assets	$ 23,000
Derivative contract, weighted average maturity (in months)	47 months
Notional amount of interest rate swap agreements added during the period	$ 200,000
Number of matured or terminated interest rate swap agreements \| item	2
Notional amount of swap agreements matured or terminated during period	$ 150,000
Number of new swap agreements \| item	4
TBA Agency MBS
Derivative [Line Items]
Fair value of derivative assets	$ 4,422	$ 6,015
Minimum \| Interest rate swap agreements
Derivative [Line Items]
Fixed interest rate	1.287%
Minimum \| TBA Agency MBS
Derivative [Line Items]
Fixed interest rate	4.00%
Maximum \| Interest rate swap agreements
Derivative [Line Items]
Fixed interest rate	3.2205%
Maximum \| TBA Agency MBS
Derivative [Line Items]
Fixed interest rate	4.50%

Aggregate amount of swaps matured or terminated in period.

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Notional amount of interest rate swap agreements added during the period.

+ References

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Number of interest rate derivative instruments added.

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Number of interest rate derivative instruments matured or terminated.

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
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- Definition

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

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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.

+ References

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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.

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- Definition

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.

+ References

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- Definition

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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