Debt - Components of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total debt	$ 2,354,066	$ 2,229,220
Unsecured debt \| Revolving credit facilities
Debt Instrument [Line Items]
Debt	290,000	165,000
Unsecured debt \| Revolving credit facilities \| Senior unsecured credit facility
Debt Instrument [Line Items]
Debt	290,000	165,000
Unsecured debt \| Revolving credit facilities \| PHL unsecured credit facility
Debt Instrument [Line Items]
Debt	0	0
Unsecured debt \| Unsecured term loans
Debt Instrument [Line Items]
Debt	1,975,000	1,975,000
Deferred financing costs, net	(10,499)	(10,343)
Total debt	1,964,501	1,964,657
Borrowings, fixed interest rate	$ 1,600,000	$ 1,600,000
Weighted-average fixed interest rate	4.21%	3.43%
Amount of debt bearing variable interest	$ 345,000	$ 345,000
Weighted-average floating interest rate	2.46%	3.32%
Unsecured debt \| Unsecured term loans \| First Term Loan
Debt Instrument [Line Items]
Debt	$ 300,000	$ 300,000
Unsecured debt \| Unsecured term loans \| Second Term Loan
Debt Instrument [Line Items]
Debt	65,000	65,000
Unsecured debt \| Unsecured term loans \| Fourth Term Loan
Debt Instrument [Line Items]
Debt	110,000	110,000
Unsecured debt \| Unsecured term loans \| Sixth Term Loan
Debt Instrument [Line Items]
Debt	1,500,000	1,500,000
Unsecured debt \| Unsecured term loans \| Tranche 2021
Debt Instrument [Line Items]
Debt	57,400	300,000
Unsecured debt \| Unsecured term loans \| Tranche 2021 Extended
Debt Instrument [Line Items]
Debt	242,600	0
Unsecured debt \| Unsecured term loans \| Tranche 2022
Debt Instrument [Line Items]
Debt	400,000	400,000
Unsecured debt \| Unsecured term loans \| Tranche 2023
Debt Instrument [Line Items]
Debt	400,000	400,000
Unsecured debt \| Unsecured term loans \| Tranche 2024
Debt Instrument [Line Items]
Debt	400,000	400,000
Senior unsecured notes
Debt Instrument [Line Items]
Debt	100,000	100,000
Deferred financing costs, net	(435)	(437)
Total debt	$ 99,565	99,563
Senior unsecured notes \| Series A Notes
Debt Instrument [Line Items]
Interest Rate	4.70%
Debt	$ 60,000	60,000
Senior unsecured notes \| Series B Notes
Debt Instrument [Line Items]
Interest Rate	4.93%
Debt	$ 40,000	$ 40,000

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.

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=120520924&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=120400017&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=120391452&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=120398452&loc=d3e534808-122878

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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=120391452&loc=d3e13212-122682

+ Details

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Balance Type:	na
Period Type:	instant

- 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.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of unamortized debt discount (premium) and debt issuance costs.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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=120520924&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=120400017&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=120398452&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=120391452&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

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- Definition

+ References

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant