CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 284,855	$ 271,940	$ 246,283
Adjustments to net income:
Depreciation and amortization	409,215	374,661	306,769
Income from discontinued operations		(2,800)	(65,670)
Amortization of share-based compensation	10,391	11,959	20,785
Non-cash rental adjustments	(8,607)	(6,848)	(5,554)
Amortization of net premiums on mortgages payable	(7,482)	(12,891)	(9,481)
Amortization of deferred financing costs	9,044	8,335	9,364
Loss (gain) on interest rate swaps	3,043	1,349	(878)
Gain on sales of real estate	(22,243)	(39,205)
Provisions for impairment on real estate	10,560	4,126	290
Change in assets and liabilities
Accounts receivable and other assets	(2,641)	(3,064)	(2,116)
Accounts payable, accrued expenses and other liabilities	6,168	20,130	19,114
Net cash provided by operating activities	692,303	627,692	518,906
CASH FLOWS FROM INVESTING ACTIVITIES
Investment in real estate	(1,266,885)	(1,228,243)	(1,429,483)
Improvements to real estate, including leasing costs	(11,541)	(6,032)	(8,507)
Proceeds from sales of real estate:
Continuing operations	65,817	88,688	8
Discontinued operations		6,918	126,785
Collection (issuance) of loans receivable		350	(10,656)
Restricted escrow deposits for Section 1031 tax-deferred exchanges and pending acquisitions	33,554	(36,540)	(10,158)
Net cash used in investing activities	(1,179,055)	(1,174,859)	(1,332,011)
CASH FLOWS FROM FINANCING ACTIVITIES
Cash distributions to common stockholders	(533,238)	(479,256)	(409,222)
Cash dividends to preferred stockholders	(27,080)	(38,300)	(41,930)
Borrowings on line of credit	1,448,000	1,672,321	2,624,700
Payments on line of credit	(1,433,000)	(1,577,321)	(2,654,700)
Proceeds from notes and bonds payable issued		598,594	750,000
Principal payments on notes payable	(150,000)		(100,000)
Principal payments on mortgages payable	(198,353)	(85,208)	(32,603)
Proceeds from term loans	250,000		70,000
Repayment of American Realty Capital Trust, Inc., or ARCT, line of credit			(317,207)
Repayment of ARCT term loan			(235,000)
Proceeds from common stock offerings, net	793,559	528,615	1,133,574
Redemption of preferred units	(6,750)
Redemption of preferred stock		(220,000)
Distributions to noncontrolling interests	(1,679)	(1,844)	(1,216)
Debt issuance costs	(10,259)	(5,505)	(10,666)
Proceeds from dividend reinvestment and stock purchase plan	363,029	158,462	55,806
Proceeds from At-the-Market (ATM) program	36,348
Other items, including shares withheld upon vesting	(7,383)	(9,796)	(13,422)
Net cash provided by financing activities	523,194	540,762	818,114
Net increase (decrease) in cash and cash equivalents	36,442	(6,405)	5,009
Cash and cash equivalents, beginning of period	3,852	10,257	5,248
Cash and cash equivalents, end of period	$ 40,294	$ 3,852	$ 10,257