Unsecured Line of Credit Payable - Narrative (Details)	3 Months Ended
	Mar. 31, 2019 USD ($) extension_option	Dec. 31, 2018 USD ($)	Mar. 29, 2018 USD ($)	Jul. 22, 2016 USD ($)	Sep. 15, 2015 USD ($)
Interest Rate Swap
Line of Credit Facility [Line Items]
Derivative, notional amount	$ 400,000,000
2018 Term Loan
Line of Credit Facility [Line Items]
Debt instrument, fixed interest rate (percent)	2.87%
LIBOR
Line of Credit Facility [Line Items]
Debt instrument variable rate (percent)	2.49%
Line of Credit
Line of Credit Facility [Line Items]
Commitment fee (percent)	0.20%
Interest rate during period (percent)	1.00%
Line of Credit | Minimum
Line of Credit Facility [Line Items]
Commitment fee (percent)	0.10%
Line of Credit | Maximum
Line of Credit Facility [Line Items]
Commitment fee (percent)	0.30%
Line of Credit | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	1.00%
Line of Credit | LIBOR | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.775%
Line of Credit | LIBOR | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	1.55%
Line of Credit | Base Rate | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.00%
Line of Credit | Base Rate | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.55%
Line of Credit | Federal Funds Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.50%
2015 Term Loan
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 150,000,000
2015 Term Loan | Interest Rate Swap
Line of Credit Facility [Line Items]
Derivative, notional amount					$ 150,000,000
Derivative, fixed interest rate (percent)					2.72%
2018 Term Loan
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 250,000,000
2018 Term Loan | Interest Rate Swap
Line of Credit Facility [Line Items]
Derivative, fixed interest rate (percent)			2.87%
2018 Term Loan A | Interest Rate Swap
Line of Credit Facility [Line Items]
Derivative, notional amount			$ 150,000,000	$ 150,000,000
Derivative, fixed interest rate (percent)			2.31%
2018 Term Loan A | LIBOR | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.85%
2018 Term Loan A | LIBOR | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	1.75%
2018 Term Loan A | Base Rate | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.00%
2018 Term Loan A | Base Rate | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.75%
2018 Term Loan B
Line of Credit Facility [Line Items]
Derivative, notional amount			$ 100,000,000
2018 Term Loan B | Interest Rate Swap
Line of Credit Facility [Line Items]
Derivative, notional amount			$ 100,000,000
Derivative, fixed interest rate (percent)			3.71%
Credit facility 2018
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	$ 1,500,000,000.0
Credit facility 2018 | Line of Credit
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity	$ 700,000,000.0
Debt instrument, term	4 years
Debt instrument, maturity date	Mar. 29, 2022
Number of extensions allowed | extension_option	2
Term of extension	6 months
Credit facility 2018 | 2015 Term Loan
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 150,000,000
Credit facility 2018 | 2018 Term Loan
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 250,000,000
Credit facility 2015 | Line of Credit
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		$ 600,000,000