Debt - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Debt outstanding	$ 2,763,207,000
Estimated fair value of debt	164,300,000	$ 167,100,000
Unrealized gain (loss) on derivative instruments	(2,907,000)	6,001,000	$ 2,438,000
(Gain) loss on derivative instruments	0	265,000	283,000
Interest rate swaps
Line of Credit Facility [Line Items]
Derivative instruments, asset position, fair value	15,100,000
Unrealized gain (loss) on derivative instruments	(2,900,000)	6,000,000
(Gain) loss on derivative instruments	0	300,000	300,000
Expected reclassifications in next 12 months	3,400,000
Interest rate swaps | Interest expense
Line of Credit Facility [Line Items]
Reclassification from AOCI to interest expense	700,000	3,400,000	$ 6,200,000
Letters of credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity	30,000,000
Unsecured debt | Revolving credit facilities
Line of Credit Facility [Line Items]
Debt outstanding	170,000,000	45,000,000
Unsecured debt | Senior unsecured credit facility | Revolving credit facilities
Line of Credit Facility [Line Items]
Maximum borrowing capacity	650,000,000
Debt outstanding	170,000,000	45,000,000
Remaining borrowing capacity	480,000,000
Maximum borrowing capacity potential increase (up to)	$ 1,300,000,000.0
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
Debt outstanding	0	0
Remaining borrowing capacity	$ 10,000,000
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%
Senior unsecured notes
Line of Credit Facility [Line Items]
Debt outstanding	$ 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
Stated interest rate	4.70%
Senior unsecured notes | Series B Notes
Line of Credit Facility [Line Items]
Debt outstanding	$ 40,000,000	$ 40,000,000
Stated interest rate	4.93%