Schedule III - Real Estate and Accumulated Depreciation - Activity in Real Estate Facilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Real estate, gross:
Balance at end of year	$ 8,754,269
Accumulated depreciation:
Balance at beginning of year	1,060,060
Balance at end of year	1,262,438	$ 1,060,060
Net real estate assets:
Net real estate assets	7,491,831	7,132,431	$ 6,770,447
Aggregate cost of real estate for U.S. federal income tax purposes	7,306,350
Operating facilities
Real estate, gross:
Balance at beginning of year	8,158,741	7,649,448	6,392,487
Acquisitions	459,223	628,391	1,159,304
Improvements	64,336	71,090	92,480
Transfers from construction in progress (to operating facilities)	49,449	19,079	26,400
Dispositions and other	(22,434)	(209,267)	(21,223)
Balance at end of year	8,709,315	8,158,741	7,649,448
Accumulated depreciation:
Balance at beginning of year	1,060,060	900,861	728,087
Depreciation expense	203,030	185,903	174,906
Dispositions and other	(652)	(26,704)	(2,132)
Balance at end of year	1,262,438	1,060,060	900,861
Real estate under development/redevelopment
Real estate, gross:
Balance at beginning of year	33,750	21,860	24,909
Current development	60,677	33,484	23,404
Transfers from construction in progress (to operating facilities)	(49,449)	(19,079)	(26,400)
Dispositions and other	(24)	(2,515)	(53)
Balance at end of year	$ 44,954	$ 33,750	$ 21,860