Debt - Narrative (Details) - USD ($)		3 Months Ended		6 Months Ended
	Jul. 18, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Line of Credit Facility [Line Items]
Letters of credit outstanding		$ 2,300,000		$ 2,300,000		$ 0
Repayments of debt				181,219,000	$ 1,175,000
Estimated fair value of debt		167,400,000		167,400,000		164,300,000
Unrealized gain (loss) on derivative instruments		(21,089,000)	$ 2,012,000	(30,128,000)	7,290,000
Interest rate swaps
Line of Credit Facility [Line Items]
Derivative instruments, asset position, fair value		1,800,000		1,800,000
Derivative instruments, liability position, fair value		20,200,000		20,200,000
Unrealized gain (loss) on derivative instruments		(21,100,000)	2,000,000.0	(30,100,000)	7,300,000
Expected reclassifications in next 12 months		6,500,000		6,500,000
Interest rate swaps | Interest expense
Line of Credit Facility [Line Items]
Reclassification of gain (loss) from AOCI to interest expense		(2,300,000)	$ (200,000)	(4,800,000)	$ 100,000
Letters of credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity		30,000,000.0		30,000,000.0
Unsecured debt | Revolving credit facilities
Line of Credit Facility [Line Items]
Debt outstanding		0		0		170,000,000
Unsecured debt | Unsecured term loans
Line of Credit Facility [Line Items]
Debt outstanding		2,245,000,000		2,245,000,000		2,425,000,000
Unsecured debt | Senior unsecured credit facility | Revolving credit facilities
Line of Credit Facility [Line Items]
Maximum borrowing capacity		650,000,000.0		650,000,000.0
Debt outstanding		0		0		170,000,000
Remaining borrowing capacity		650,000,000.0		650,000,000.0
Maximum borrowing capacity potential increase (up to)		1,300,000,000		$ 1,300,000,000
Unsecured debt | Senior unsecured credit facility | Revolving credit facilities | Minimum
Line of Credit Facility [Line Items]
Unused commitment fee annual rate				0.20%
Unsecured debt | Senior unsecured credit facility | Revolving credit facilities | Minimum | LIBOR
Line of Credit Facility [Line Items]
Credit facility borrowings LIBOR rate plus				1.45%
Unsecured debt | Senior unsecured credit facility | Revolving credit facilities | Maximum
Line of Credit Facility [Line Items]
Unused commitment fee annual rate				0.30%
Unsecured debt | Senior unsecured credit facility | Revolving credit facilities | Maximum | LIBOR
Line of Credit Facility [Line Items]
Credit facility borrowings LIBOR rate plus				2.25%
Unsecured debt | PHL unsecured credit facility | Revolving credit facilities
Line of Credit Facility [Line Items]
Maximum borrowing capacity		10,000,000.0		$ 10,000,000.0
Debt outstanding		0		0		0
Remaining borrowing capacity		10,000,000.0		$ 10,000,000.0
Unsecured debt | PHL unsecured credit facility | Revolving credit facilities | Minimum | LIBOR
Line of Credit Facility [Line Items]
Credit facility borrowings LIBOR rate plus				1.45%
Unsecured debt | PHL unsecured credit facility | Revolving credit facilities | Maximum | LIBOR
Line of Credit Facility [Line Items]
Credit facility borrowings LIBOR rate plus				2.25%
Unsecured debt | Sixth Term Loan Tranche 2020 | Unsecured term loans
Line of Credit Facility [Line Items]
Debt outstanding		70,000,000		$ 70,000,000		250,000,000
Repayments of debt				180,000,000.0
Senior unsecured notes
Line of Credit Facility [Line Items]
Debt outstanding		100,000,000		100,000,000		100,000,000
Senior unsecured notes | Series A Notes
Line of Credit Facility [Line Items]
Debt outstanding		$ 60,000,000		$ 60,000,000		60,000,000
Stated interest rate		4.70%		4.70%
Senior unsecured notes | Series B Notes
Line of Credit Facility [Line Items]
Debt outstanding		$ 40,000,000		$ 40,000,000		$ 40,000,000
Stated interest rate		4.93%		4.93%
Subsequent event | Unsecured debt | Sixth Term Loan Tranche 2020 | Unsecured term loans
Line of Credit Facility [Line Items]
Repayments of debt	$ 70,000,000.0