Senior Unsecured Notes and Secured Debt - Summary of Principal Activity (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)
Amount
Debt issued	$ 1,208,241	$ 1,588,549
Debt issued	0	44,921
Ending balance	13,564,113
Senior unsecured notes
Amount
Beginning balance	11,509,533	10,427,562
Debt issued	1,250,000	1,600,000
Debt extinguished	(1,533,752)	0
Foreign currency	27,204	(114,851)
Ending balance	$ 11,252,985	$ 11,912,711
Weighted Avg. Interest Rate
Beginning balance	3.67%	4.03%
Debt issued	0.0250	0.0189
Debt extinguished	0.0242	0
Foreign currency	0.0357	0.0430
Ending balance	3.71%	3.65%
Secured debt
Amount
Beginning balance	$ 2,378,073	$ 2,993,342
Debt issued	0	44,921
Debt extinguished	(66,593)	(314,631)
Principal payments	(31,670)	(30,709)
Foreign currency	31,318	(64,934)
Ending balance	$ 2,311,128	$ 2,627,989
Weighted Avg. Interest Rate
Beginning balance	3.27%	3.63%
Debt issued	0	0.0258
Debt extinguished	0.0601	0.0294
Principal payments	0.0348	0.0355
Foreign currency	0.0289	0.0313
Ending balance	3.10%	3.09%