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Debt Obligations (Textual) (Details) |  |  |  |  | 12 Months Ended
--- | --- | --- | --- | --- | ---
Jul. 17, 2018 USD ($) Extension | Dec. 18, 2017 USD ($) | Nov. 16, 2017 USD ($) | Nov. 09, 2017 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |
Line of Credit |  |  |  |  | $ 92,500,000 | $ 0 |
Loss on early extinguishment of debt |  |  |  |  | (105,000) | (3,933,000) | $ (66,590,000)
Extinguishment of Debt, Amount |  |  |  |  | $ 0 | $ 325,000,000.0 | $ 0
Prior Revolving Credit Facilty [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt instrument maturity date | May 15, 2019 |  |  |  |  |  |
Revolving Credit Facility [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Long-term Debt, Weighted Average Interest Rate |  |  |  |  | 3.24% | 2.28% |
Line of Credit |  |  |  |  | $ 92,500,000 | $ 0 |
Effective interest rate on credit facility |  |  |  |  | 3.61% |  |
Interest expense borrowings |  |  |  |  | $ 1,000,000.0 | $ 2,600,000 |
Revolving Credit Facility [Member] | New Credit Facility [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Maximum borrowing capacity | $ 600,000,000.0 |  |  |  |  |  |
Debt instrument maturity date | Jul. 15, 2022 |  |  |  |  |  |
Debt instrument, number of extensions | Extension | 2 |  |  |  |  |  |
Debt instrument, maturity extension period | 6 months |  |  |  |  |  |
Debt financing costs | $ 2,700,000 |  |  |  |  |  |
Minimum Credit Spread on a LIBOR Rate Loan |  |  |  |  | 0.00% |  |
Maximum Credit Spread on a LIBOR Rate Loan |  |  |  |  | 0.45% |  |
Commitment fee percentage |  |  |  |  | 0.25% |  |
Minimum fixed charge coverage ratio |  |  |  |  | 1.5 |  |
Maximum leverage ratio |  |  |  |  | 0.60 |  |
Maximum unsecured indebtedness to unencumbered asset value ratio |  |  |  |  | 0.60 |  |
Maximum secured indebtedness to total asset value ratio |  |  |  |  | 0.40 |  |
Minimum unencumbered cash flow to interest expense on unsecured debt ratio |  |  |  |  | 1.75 |  |
Maximum percent of payments of dividends and distributions |  |  |  |  | 95.00% |  |
Revolving Credit Facility [Member] | New Credit Facility [Member] | Minimum [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Commitment fee percentage |  |  |  |  | 0.125% |  |
Revolving Credit Facility [Member] | New Credit Facility [Member] | Maximum [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Commitment fee percentage |  |  |  |  | 0.30% |  |
Revolving Credit Facility [Member] | New Credit Facility [Member] | LIBOR [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Variable interest rate |  |  |  |  | 1.10% |  |
Basis spread on variable rate |  |  |  |  | 1.00% |  |
Revolving Credit Facility [Member] | New Credit Facility [Member] | LIBOR [Member] | Minimum [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Variable interest rate |  |  |  |  | 0.775% |  |
Revolving Credit Facility [Member] | New Credit Facility [Member] | LIBOR [Member] | Maximum [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Variable interest rate |  |  |  |  | 1.45% |  |
Revolving Credit Facility [Member] | New Credit Facility [Member] | Federal Funds Rate [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Basis spread on variable rate |  |  |  |  | 0.50% |  |
Secured Debt [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Long-term Debt, Weighted Average Interest Rate |  |  |  |  | 4.05% | 4.04% | 4.03%
Long-term Debt, Gross |  |  |  |  | $ 323,032,000 | $ 320,107,000 |
Unsecured Debt [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Long-term Debt, Gross |  |  |  |  | $ 1,721,110,000 | 1,628,610,000 |
Unsecured Debt [Member] | $450.0M 3.95% Guaranteed Notes due 2027 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt instrument maturity date |  |  |  |  | Oct. 01, 2024 |  |
Long-term Debt, Gross |  |  |  | $ 450,000,000.0 | $ 450,000,000 | 450,000,000 |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  | 3.95% |  |  |
Debt instrument, Unamortized discount, Percent of face amount |  |  |  | 99.25% |  |  |
Debt instrument, Yield to maturity |  |  |  | 4.04% |  |  |
Debt instrument, Yield to maturity spread at time of pricing |  |  |  | 1.70% |  |  |
Treasury note rate term |  |  |  | 10 years |  |  |
Unsecured Debt [Member] | $350M 3.95% Guaranteed Notes due 2023 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt instrument maturity date |  |  |  |  | Apr. 15, 2018 |  |
Long-term Debt, Gross |  |  |  |  | $ 350,000,000 | 350,000,000 |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  | 3.95% |  |  |
Debt Instrument, Face Amount |  |  |  | $ 100,000,000.0 |  |  |
Debt instrument, Unamortized discount, Percent of face amount |  |  |  | 102.497% |  |  |
Debt instrument, Yield to maturity |  |  |  | 3.40% |  |  |
Debt instrument, Yield to maturity spread at time of pricing |  |  |  | 1.40% |  |  |
Treasury note rate term |  |  |  | 5 years |  |  |
Unsecured Debt [Member] | Notes 2027 and 2023 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Unamortized Discount |  |  |  |  |  | 3,400,000 |
Debt Instrument, Unamortized Premium |  |  |  |  |  | $ 2,500,000 |
Proceeds from Notes Payable |  |  |  | $ 546,600,000 |  |  |
Unsecured Debt [Member] | Notes 2018 [Member] |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |
Debt Instrument, Repurchased Face Amount |  | $ 211,600,000 | $ 115,100,000 |  |  |  |
Repayments of debt |  |  | 113,400,000 |  |  |  |
Repayment of prepayment penalties |  | 2,300,000 | 1,200,000 |  |  |  |
Repayment of accrued interest |  | 1,800,000 | 500,000 |  |  |  |
Loss on early extinguishment of debt |  | (2,500,000) | $ (1,400,000) |  |  |  |
Debt instrument, cash redemption price |  | $ 215,700,000 |  |  |  |  |

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- Definition Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt. + 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)(1) -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(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 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 4: 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 + Details
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- Definition Contractual interest rate for funds borrowed, under the debt 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(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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- Definition Face (par) amount of the original debt instrument that was repurchased. + References No definition available. + Details
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- Definition Amount, after accumulated amortization, of debt discount. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + 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 The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used. + References No definition available. + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + 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 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Weighted average interest rate of long-term debt outstanding calculated at point in time. + References No definition available. + Details
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