Senior Unsecured Notes and Secured Debt - Summary of Principal Activity (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)
Amount
Debt issued, unsecured	$ 0	$ 1,036,964
Debt issued, secured	44,921	247,163
Ending balance	13,211,511
Senior Unsecured Notes
Amount
Beginning balance	10,427,562	9,699,984
Debt issued, unsecured	0	1,050,000
Debt extinguished	0	(1,050,000)
Foreign currency	(120,689)	37,553
Ending balance	$ 10,306,873	$ 9,737,537
Weighted Avg. Interest Rate
Beginning balance	4.03%	4.48%
Debt issued	0	0.0389
Debt extinguished	0	0.0498
Foreign currency	0.0415	0.0433
Ending balance	3.97%	4.35%
Secured Debt
Amount
Beginning balance	$ 2,993,342	$ 2,485,711
Debt issued, secured	44,921	247,163
Debt assumed	0	42,000
Debt extinguished	(16,040)	(114,570)
Principal payments	(15,526)	(13,543)
Foreign currency	(102,059)	26,197
Ending balance	$ 2,904,638	$ 2,672,958
Weighted Avg. Interest Rate
Beginning balance	3.63%	3.90%
Debt issued	0.0258	0.0368
Debt assumed	0	0.0462
Debt extinguished	0.0451	0.0496
Principal payments	0.0378	0.0385
Foreign currency	0.0327	0.0333
Ending balance	3.63%	3.84%