Schedule III - Real Estate and Accumulated Depreciation - Activity in Real Estate Facilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Real estate, gross:
Balance at end of year	$ 9,575,231
Accumulated depreciation:
Balance at end of year	1,681,429
Net real estate assets:
Net non-lease real estate assets	7,893,802	$ 7,696,864	$ 7,491,831
Aggregate cost of real estate for U.S. federal income tax purposes	7,817,038
Operating facilities
Real estate, gross:
Balance at beginning of year	9,129,558	8,709,315	8,158,741
Acquisitions	255,235	303,588	459,223
Improvements	66,693	68,459	64,336
Transfers from construction in progress (to operating facilities)	40,988	59,614	49,449
Dispositions and other	15,314	(11,418)	(22,434)
Balance at end of year	9,507,788	9,129,558	8,709,315
Accumulated depreciation:
Balance at beginning of year	1,473,851	1,262,438	1,060,060
Depreciation expense	217,364	212,202	203,030
Dispositions and other	(9,786)	(789)	(652)
Balance at end of year	1,681,429	1,473,851	1,262,438
Real estate under development/redevelopment
Real estate, gross:
Balance at beginning of year	41,157	44,954	33,750
Current development	67,274	55,817	60,677
Transfers from construction in progress (to operating facilities)	(40,988)	(59,614)	(49,449)
Dispositions and other	0	0	(24)
Balance at end of year	67,443	$ 41,157	$ 44,954
Right of use asset - finance lease
Real estate, gross:
Balance at end of year	58,145
Accumulated depreciation:
Balance at end of year	$ 566