Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible assets:
Goodwill	$ 1,034,641	$ 1,033,225
Accumulated amortization	(861,452)	(769,558)
Net intangible assets	$ 1,747,074	$ 1,810,079
Remaining weighted average amortization period in years	21 years 8 months 12 days	21 years 6 months
Intangible liabilities:
Below market lease intangibles	$ 359,099	$ 345,103
Other lease intangibles	40,141	40,843
Accumulated amortization	(160,965)	(133,468)
Purchase option intangibles	3,568	3,568
Net intangible liabilities	$ 241,843	$ 256,046
Below market leases, remaining weighted average amortization period	13 years 8 months 12 days	14 years 1 month 6 days
Other lease intangibles, remaining weighted average amortization period	40 years 9 months 18 days	38 years 6 months
Net intangible liabilities, remaining weighted average amortization period	15 years 7 months 6 days	15 years 10 months 24 days
Intangibles
Net amortization expense	$ 67,200	$ 104,500	$ 142,700
Estimated net amortization of the intangibles during 2018	55,591
Estimated net amortization of the intangibles during 2019	46,137
Estimated net amortization of the intangibles during 2020	40,085
Estimated net amortization of the intangibles during 2021	37,180
Estimated net amortization of the intangibles during 2022	30,580
Above Market Lease Intangibles
Intangible assets:
Intangible assets	$ 184,775	$ 184,993
Remaining weighted average amortization period in years	7 years	6 years 10 months 24 days
In-Place and Other Lease Intangibles
Intangible assets:
Intangible assets	$ 1,353,220	$ 1,325,636
Remaining weighted average amortization period in years	23 years 7 months 6 days	23 years 7 months 6 days
Other Intangibles
Intangible assets:
Other finite-lived intangible assets	$ 35,890	$ 35,783
Remaining weighted average amortization period in years	12 years 3 months 18 days	11 years 3 months 18 days
Triple-Net Leased Properties
Intangible assets:
Goodwill	$ 305,261