Investments in Affiliates - Equity Method Investment Summarized Balance Sheet Information (Details) - Joint Venture Unconsolidated [Member] - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Investments In And Advances To Affiliates [Line Items]
Equity Method Investment, Summarized Financial Information, Current Assets		$ 138,887	$ 31,320	$ 26,442
Equity Method Investment, Summarized Financial Information, Noncurrent Assets		168,402	129,039	137,272
Equity Method Investment, Summarized Financial Information, Assets		307,289	160,359	163,714
Equity Method Investment, Summarized Financial Information, Current Liabilities		71,940	30,131	32,463
Equity Method Investment, Summarized Financial Information, Long-term Liabilities	[1]	46,961	31,636	32,761
Equity Method Investment, Summarized Financial Information, Total Liabilities		118,901	61,767	65,224
Equity Method Investments Summarized Financial Information Net Assets		188,388	98,592	98,490
Other Affiliates [Member]
Investments In And Advances To Affiliates [Line Items]
Equity Method Investment, Summarized Financial Information, Assets		307,300
Equity Method Investments		$ 84,840	$ 38,469	$ 39,946

[1] The balance primarily relates to debt associated with our real estate investments. The increase in the balance since December 31, 2017 is related to debt of our foreign affiliates associated with purchase of equipment and buildings.