Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value, by Balance Sheet Grouping [Table Text Block]

All financial instruments of the Company are reflected in the accompanying Consolidated Balance Sheets at amounts which, in management's estimation, reasonably approximates their fair values, except for the following:

	December 31,
	2018			2017
(in thousands)	Carrying Amount		Fair Value	Carrying Amount		Fair Value
Financial assets:
Notes receivable (1)	$	—	—	$	15,803	15,660
Financial liabilities:
Notes payable	$	3,006,478	2,961,769	$	2,971,715	3,058,044
Unsecured credit facilities	$	708,734	710,902	$	623,262	625,000
(1)  Notes receivable are included in Tenant and other receivables, net on the Consolidated Balance Sheets.

Fair Value, Assets Measured on Recurring Basis [Table Text Block]

The following table presents the placement in the fair value hierarchy of assets and liabilities that are measured at fair value on a recurring basis:

	Fair Value Measurements as of December 31, 2018
				Quoted Prices in Active Markets for Identical Assets	Significant Other Observable Inputs		Significant Unobservable Inputs
(in thousands)	Balance			(Level 1)	(Level 2)		(Level 3)
Assets:
Securities	$	33,354		33,354	—		—
Available-for-sale debt securities	7,933			—	7,933		—
Interest rate derivatives	17,482			—	17,482		—
Total	$	58,769		33,354	25,415		—
Liabilities:
Interest rate derivatives	$	(5,491	)	—	(5,491	)	—

	Fair Value Measurements as of December 31, 2017
				Quoted Prices in Active Markets for Identical Assets	Significant Other Observable Inputs		Significant Unobservable Inputs
(in thousands)	Balance			(Level 1)	(Level 2)		(Level 3)
Assets:
Securities	$	31,662		31,662	—		—
Available-for-sale debt securities	9,974			—	9,974		—
Interest rate derivatives	14,515			—	14,515		—
Total	$	56,151		31,662	24,489		—
Liabilities:
Interest rate derivatives	$	(177	)	—	(177	)	—