Senior Unsecured Notes and Secured Debt - Summary of Principal Activity (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Amount
Debt issued, unsecured	$ 3,253,516	$ 2,825,898
Debt issued, secured	318,854	44,606
Ending balance	12,456,291
Senior Unsecured Notes
Amount
Beginning balance	9,699,984	8,417,447
Debt issued, unsecured	3,260,000	2,850,000
Debt extinguished	(3,107,500)	(1,450,000)
Foreign currency	(35,208)	(63,751)
Ending balance	$ 9,817,276	$ 9,753,696
Weighted Avg. Interest Rate
Beginning balance	4.48%	4.31%
Debt issued	0.0347	0.0457
Debt extinguished	0.0447	0.0346
Foreign currency	0.0435	0.0430
Ending balance	4.12%	4.45%
Secured Debt
Amount
Beginning balance	$ 2,485,711	$ 2,618,408
Debt issued, secured	318,854	44,606
Debt assumed	42,000	99,552
Debt extinguished	(193,604)	(196,573)
Principal payments	(40,348)	(42,294)
Foreign currency	26,402	(43,944)
Ending balance	$ 2,639,015	$ 2,479,755
Weighted Avg. Interest Rate
Beginning balance	3.90%	3.76%
Debt issued	0.0351	0.0338
Debt assumed	0.0462	0.0430
Debt extinguished	0.0437	0.0566
Principal payments	0.0369	0.0391
Foreign currency	0.0320	0.0329
Ending balance	3.66%	3.79%