Senior Unsecured Notes and Secured Debt - Summary of Principal Activity (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)
Amount
Beginning balance
Debt issued	$ 1,588,549	$ 2,036,964
Debt issued	44,921	295,969
Ending balance	14,540,700
Senior unsecured notes
Amount
Beginning balance	10,427,562	9,699,984
Debt issued	1,600,000	2,050,000
Debt extinguished	0	(1,050,000)
Foreign currency	(114,851)	11,572
Ending balance	$ 11,912,711	$ 10,711,556
Weighted Avg. Interest Rate
Beginning balance	4.03%	4.48%
Debt issued	0.0189	0.0358
Debt extinguished	0	0.0498
Foreign currency	0.0430	0.0352
Ending balance	3.65%	4.24%
Secured debt
Amount
Beginning balance	$ 2,993,342	$ 2,485,711
Debt issued	44,921	295,969
Debt assumed	0	42,000
Debt extinguished	(314,631)	(151,473)
Principal payments	(30,709)	(27,227)
Foreign currency	(64,934)	45,002
Ending balance	$ 2,627,989	$ 2,689,982
Weighted Avg. Interest Rate
Beginning balance	3.63%	3.90%
Debt issued	0.0258	0.0352
Debt assumed	0	0.0462
Debt extinguished	0.0294	0.0442
Principal payments	0.0355	0.0374
Foreign currency	0.0313	0.0337
Ending balance	3.09%	3.84%