Investment in Storage Facilities and Intangible Assets - Summary of Activity in Storage Facilities (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Cost:
Beginning balance	$ 4,398,939
Acquisition of storage facilities	108,356
Improvements and equipment additions	39,613
Net decrease in construction in progress	(1,988)
Dispositions	(3,309)
Ending balance	4,541,611
Accumulated Depreciation:
Beginning balance	704,681
Additions during the period	51,440
Dispositions	(2,540)
Ending balance	$ 753,581