Intangible Assets and Intangible Liabilities - Summary of Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Intangible assets:
Gross amount	$ 553,063	$ 579,066
Accumulated amortization	(200,857)	(166,841)
Intangible assets, Net	352,206	412,225
Intangible liabilities:
Gross amount	205,101	208,367
Accumulated amortization	(75,073)	(55,349)
Intangible Liabilities, Net	$ 130,028	$ 153,018