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Derivative Financial Instruments - Summary of Aggregate Amount and Estimated Net Fair Value of Derivative Instruments (Detail) - USD ($) | Dec. 31, 2018 | Nov. 30, 2018 | Oct. 17, 2018 | Dec. 31, 2017 | Nov. 17, 2017 | Jun. 24, 2016
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Derivative Instruments Gain Loss [Line Items] |  |  |  |  |  |
Derivative, notional amount | $ 400,000,000 |  |  | $ 250,000,000 |  |
Fair Value of Assets | 8,307,000 |  |  | 7,291,000 |  |
Fair Value of Assets |  |  |  | 7,291,000 |  |
Interest Rate Swap |  |  |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |  |  |
Derivative, notional amount |  |  |  |  |  | $ 150,000,000
Cash Flow Hedge |  |  |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |  |  |
Derivative, notional amount | 400,000,000 |  |  | 200,000,000 |  |
Fair Value of Assets | 8,307,000 |  |  | 5,997,000 |  |
Cash Flow Hedge | Interest Rate Swap |  |  |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |  |  |
Derivative, notional amount | 150,000,000 |  |  | 150,000,000 |  |
Fair Value of Assets | 4,751,000 |  |  | 4,700,000 |  |
Cash Flow Hedge | Interest Rate Collar |  |  |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |  |  |
Derivative, notional amount | 250,000,000 | $ 150,000,000 | $ 100,000,000 | 50,000,000 | $ 100,000,000 |
Fair Value of Assets | $ 3,556,000 |  |  | 1,297,000 |  |
Freestanding Derivatives | Interest Rate Collar |  |  |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |  |  |
Derivative, notional amount |  |  |  | 50,000,000 | $ 50,000,000 |
Fair Value of Assets |  |  |  | $ 1,294,000 |  |

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Fair value of all asset derivatives designated as cash flow hedging instruments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959 + Details
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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 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details
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