Real Estate and Other Activities - Summary of Joint Venture Designated as Held for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Real estate held for sale	$ 1,096,475
Straight-line rent receivables	661,429	$ 490,462
Other assets	315,977	256,069
Total Assets	19,711,987	$ 16,829,014
Massachusetts-based General Acute Care Hospitals [Member]
Business Acquisition [Line Items]
Real estate held for sale	1,096,475
Straight-line rent receivables	113,923
Other assets	5,917
Total Assets	$ 1,216,315