Indebtedness - Additional Information (Details) $ in Thousands, ft² in Millions				12 Months Ended
		Sep. 11, 2015 USD ($)	Jan. 29, 2014 USD ($)	Dec. 31, 2018 USD ($) ft² Property	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Oct. 31, 2017 USD ($)	Mar. 10, 2015 USD ($)
Debt Instrument [Line Items]
Loss from Retirement of Debt				$ (39)	$ (1,775)	$ 0
Long-term Debt, Gross				$ 1,306,181
2028 Private Placement Notes
Debt Instrument [Line Items]
Interest Rate				3.86%
Long-term Debt, Gross				$ 150,000	0
Effective Interest Rate				3.86%
2030 Private Placement Notes
Debt Instrument [Line Items]
Interest Rate				3.96%
Long-term Debt, Gross				$ 150,000	0
Effective Interest Rate				3.96%
2027 Private Placement Notes
Debt Instrument [Line Items]
Interest Rate				4.30%
Long-term Debt, Gross				$ 125,000	$ 125,000
Effective Interest Rate				4.30%	4.30%
2029 Private Placement Notes
Debt Instrument [Line Items]
Interest Rate				4.40%
Long-term Debt, Gross				$ 75,000	$ 75,000
Effective Interest Rate				4.40%	4.40%
2017 II Notes
Debt Instrument [Line Items]
Extinguishment of debt, amount					$ 101,871
2017 Notes
Debt Instrument [Line Items]
Extinguishment of debt, amount					54,981
2014 Unsecured Term Loan (A)
Debt Instrument [Line Items]
Debt Instrument Interest Rate Change Due to Investment Grade Rating				10 basis point
Loss from Retirement of Debt					51
Interest Rate	[1]			3.39%
Debt Instrument, term			7 years
Long-term Debt, Gross				$ 200,000	200,000
Unsecured term loan, face amount			$ 200,000
Debt instrument, interest rate terms				LIBOR plus 110 basis points
2015 Unsecured Term Loan (A)
Debt Instrument [Line Items]
Interest Rate	[1]			2.89%
Debt Instrument, term		7 years
Long-term Debt, Gross				$ 260,000	260,000
Unsecured term loan, face amount		$ 260,000
Debt instrument, interest rate terms				LIBOR plus 110 basis points
Mortgage Loans Payable
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense				$ 1,246	1,806
Extinguishment of debt, amount				157,782	36,108
Loss from Retirement of Debt				39	1,653
Net carrying value of industrial properties collateralized by mortgage loans				459,225
Long-term Debt, Gross				297,610	451,602
Mortgage Loans Payable | Assumed Mortgage
Debt Instrument [Line Items]
Assumed mortgage loan				$ 11,654
Number of industrial properties acquired | Property				3
Gross leasable area (GLA) of industrial properties acquired | ft²				0.2
Interest Rate				4.17%
Debt Instrument, term				30 years
Unsecured Credit Facility
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense				$ 3,554	4,781
Loss from Retirement of Debt					$ 71
Line of Credit Facility, current borrowing capacity							$ 725,000	$ 625,000
Line of Credit Facility, additional borrowings capacity				$ 1,000,000
Number of years of extension of the Line of Credit Facility at election				1 year
Line of Credit Facility, interest rate description				LIBOR plus 110 basis points

[1] See Note 12.