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Mortgage Notes Payable, Revolving Credit Facility, and Term Loan Facility - Additional Information (Detail) |  |  | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Oct. 27, 2017 USD ($) | Oct. 05, 2015 USD ($) | Dec. 31, 2018 USD ($) property mortgage | Dec. 31, 2017 USD ($) | Aug. 31, 2013 USD ($)
Debt Instrument [Line Items] |  |  |  |  |
Number of properties collateralized in mortgage notes payable | property |  |  | 100 |  |
Net book value of collateralized mortgage properties |  |  | $ 5,900,000 |  |
Fair value of mortgage notes payable outstanding |  |  | 444,200,000 |  |
Long-term debt |  |  | 566,059,000 | $ 542,627,000 |
Line of credit facility, maximum borrowing capacity |  |  | 75,000,000.0 |  | $ 25,000,000.0
Borrowings under revolving credit facility, net |  |  | $ 50,084,000 | 20,715,000 |
Line of credit at an interest rate (as percent) |  |  | 4.24% |  |
Weighted average interest rate on debt outstanding (as percent) |  |  | 4.59% |  |
Mortgage notes payable |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Number of mortgage notes payable | mortgage |  |  | 47 |  |
Number of properties collateralized in mortgage notes payable | property |  |  | 68 |  |
Net book value of collateralized mortgage properties |  |  | $ 643,300,000 |  |
Collateral |  |  | $ 10,200,000 |  |
Collateral (as percent) |  |  | 2.30% |  |
Number of mortgages repaid | mortgage |  |  | 2 |  |
Number of properties collateralized | property |  |  | 2 |  |
Number of long-term mortgages issued | property |  |  | 3 |  |
Number of properties to issue collateralized mortgage notes payable | property |  |  | 3 |  |
Number of long-term mortgages maturity extended | property |  |  | 4 |  |
Number of properties maturity extended collateralized mortgage notes payable | property |  |  | 9 |  |
Long-term debt |  |  | $ 441,346,000 | $ 447,380,000 |
Weighted average interest rate on debt outstanding (as percent) |  |  | 4.69% |  |
LIBOR |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Spread on LIBOR (as percent) | 2.75% |  |  |  |
Five year term loan facility |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt instrument term | 5 years |  |  |  |
Revolving credit facility |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt instrument term | 4 years |  |  |  |
Line of credit |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Line of credit facility, maximum borrowing capacity |  | $ 85,000,000.0 |  |  |
Debt instrument, fee | $ 900,000 |  |  |  |
Borrowings under revolving credit facility, net |  |  | $ 125,600,000 |  |
Letters of credit, outstanding |  |  | 2,100,000 |  |
Line of credit facility, maximum additional amount drawn |  |  | $ 32,400,000 |  |
Line of credit | Five year term loan facility |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Line of credit facility, maximum borrowing capacity |  | $ 25,000,000.0 |  |  |
Debt instrument term |  | 5 years |  |  |
Letter of credit |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Weighted average interest rate on debt outstanding (as percent) |  |  | 1.75% |  |

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- Definition Amount of contractual principal due at origination of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Paragraph Column F -Subsection 29 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 310 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-29(Column F)) -URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014 + Details
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- Definition Period of time between issuance and maturity of debt instrument, 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 The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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