Schedule III - Real Estate and Accumulated Depreciation and Amortization Notes to Schedule III (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at the beginning of year	$ 5,913,547	$ 5,236,251	$ 4,686,844
Acquisitions, completed construction and tenant improvements	833,764	717,899	601,168
Disposition of land, buildings, and leasehold interests	(91,818)	(36,633)	(50,938)
Provision for loss on impairment of real estate	(7,896)	(3,970)	(823)
Balance at the close of year	6,647,597	5,913,547	5,236,251
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at the beginning of year	624,607	513,175	418,136
Disposition of land, buildings, and leasehold interests	(16,286)	(7,377)	(9,153)
Depreciation and amortization expense	134,146	118,809	104,192
Balance at the close of year	742,467	624,607	513,175
Work in progress	24,057	61,354	$ 28,908
Mortgages payable, including unamortized premium and net of unamortized debt costs	13,878	$ 23,964
Operating Lease
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at the close of year	6,596,728
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at the close of year	739,505
Real estate, federal income tax basis	6,532,163
Direct Financing Lease
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at the close of year	0
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at the close of year	0
Real estate, federal income tax basis	2,703
Mortgage Agreement-3
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Mortgages payable, including unamortized premium and net of unamortized debt costs	$ 15,151