Intangible Assets and Liabilities Estimated Future Annual Amortization Expense (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Intangible Assets [Abstract]
2018 (amount remaining at September 30, 2018)	$ 19,547
2019	72,681
2020	52,727
2021	37,314
2022	27,160
Beyond 2022	65,663
Total intangible assets subject to amortization (accretion)	275,092	$ 95,228
2018 (amount remaining at September 30, 2018)	(1,304)
2019	(8,233)
2020	(8,028)
2021	(1,963)
2022	(459)
Beyond 2022	0
Intangible liabilities, Net	(19,987)	$ 0
2018 (amount remaining at September 30, 2018)	18,243
2019	64,448
2020	44,699
2021	35,351
2022	26,701
Beyond 2022	65,663
Total intangible assets (liabilities), net	$ 255,105