Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 397,089	$ 209,536	$ 195,896
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	182,560	133,457	115,076
Amortization of deferred financing costs	12,922	7,779	6,592
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	4,980	3,310	2,683
Non-cash interest expense related to amortization of premium on notes payable	(872)	(2,409)	(3,079)
Compensation expense related to stock-based awards	8,045	6,055	4,984
Gain on sale of real estate assets and purchase of joint venture partners' interests	(69,199)	(2,857)	(3,438)
Loss (gain) on real estate transactions and earnout from prior acquisition	(8,465)	(1,501)	2,500
Property casualty loss	0	0	1,724
Distributions from unconsolidated real estate ventures in excess of earnings	3,534	4,531	4,510
Changes in operating assets and liabilities:
Receivables from related parties and affiliated real estate joint ventures	1,367	(1,436)	71
Other assets	(2,981)	(1,172)	(1,498)
Accounts payable and accrued expenses	10,075	108	4,920
Other liabilities	208	11,928	6,640
Net cash provided by operating activities	539,263	367,329	337,581
Cash flows from investing activities:
Acquisition of SmartStop, net of cash acquired	0	(1,200,853)	0
Acquisition of real estate assets	(1,086,523)	(349,897)	(503,538)
Development and redevelopment of real estate assets	(23,279)	(26,931)	(23,528)
Proceeds from sale of real estate assets, investments in real estate ventures and other assets	60,813	800	0
Change in restricted cash	16,854	1,282	(3,794)
Investment in unconsolidated real estate ventures	(28,241)	(3,434)	0
Return of investment in unconsolidated real estate ventures	16,953	45,080	0
Purchase/issuance of notes receivable	(26,429)	(84,331)	(29,258)
Principal payments received from notes receivable	42,785	0	0
Purchase of equipment and fixtures	(4,968)	(7,380)	(4,830)
Net cash used in investing activities	(1,032,035)	(1,625,664)	(564,948)
Cash flows from financing activities:
Proceeds from the sale of common stock, net of offering costs	123,424	446,877	0
Net proceeds from the issuance of 2015 exchangeable senior notes	0	563,500	0
Repurchase of exchangeable senior notes	(22,195)	(227,212)	0
Proceeds from notes payable, unsecured term loans and lines of credit	1,900,357	2,121,802	917,664
Principal payments on notes payable, unsecured term loans and lines of credit	(1,122,442)	(1,313,570)	(533,128)
Deferred financing costs	(17,486)	(9,779)	(5,305)
Net proceeds from exercise of stock options	1,444	1,542	3,095
Proceeds from termination of interest rate cap	1,650	0	0
Purchase of interest rate cap	0	(2,884)	0
Payment of earnout from prior acquisition	(4,600)	0	0
Redemption of Operating Partnership units held by noncontrolling interests	(506)	0	(4,794)
Dividends paid on common stock	(367,818)	(269,302)	(210,091)
Distributions to noncontrolling interests	(30,997)	(24,503)	(19,134)
Net cash provided by financing activities	460,831	1,286,471	148,307
Net increase (decrease) in cash and cash equivalents	(31,941)	28,136	(79,060)
Cash and cash equivalents, beginning of the period	75,799	47,663	126,723
Cash and cash equivalents, end of the period	43,858	75,799	47,663
Supplemental schedule of cash flow information
Interest paid	122,265	89,507	75,218
Income taxes paid	14,864	1,782	3,418
Redemption of Operating Partnership units held by noncontrolling interests for common stock
Noncontrolling interests in Operating Partnership	(577)	(28,106)	(10,638)
Common stock and paid-in capital	577	28,106	10,638
Tax effect from vesting of restricted stock grants and option exercises
Other assets	2,404	1,727	3,613
Additional paid-in capital	(2,404)	(1,727)	(3,613)
Acquisitions of real estate assets
Value of Operating Partnership units issued	(74,235)	(142,399)
Notes payable assumed	(9,723)	0
Accrued construction costs and capital expenditures
Acquisition of real estate assets	8,497	2,332	2,799
Development and redevelopment of real estate assets	125	0	0
Other liabilities	(8,622)	(2,332)	(2,799)
Distribution of real estate from investments in unconsolidated real estate ventures
Real estate assets, net	25,055	0	0
Investments in unconsolidated real estate ventures	(25,055)	0	0
Disposition of real estate assets
Real estate assets, net	(7,689)	0	0
Acquisitions Of Real Estate [Member]
Acquisitions of real estate assets
Real estate assets, net	84,163	158,009	77,158
Value of Operating Partnership units issued	(74,440)	(142,399)	(38,811)
Notes payable assumed	(9,723)	0	(38,347)
Receivables from related parties and affiliated real estate joint ventures	0	(15,610)	0
Redemption Of Operating Partnership Units [Member]
Disposition of real estate assets
Operating Partnership units redeemed	7,689	0	0
Acquisition Of Other Noncontrolling Interests [Member]
Acquisition of noncontrolling interests
Operating Partnership units issued	(800)	0	0
Other noncontrolling interests	162	0	0
Additional paid-in capital	$ 638	$ 0	$ 0