Investments in Affiliates - Equity Method Investment Summarized Balance Sheet Information (Details) - Joint Venture Unconsolidated [Member] - USD ($) $ in Thousands		Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Investments In And Advances To Affiliates [Line Items]
Equity Method Investment, Summarized Financial Information, Current Assets		$ 136,953	$ 31,320	$ 25,246
Equity Method Investment, Summarized Financial Information, Noncurrent Assets		173,384	129,039	131,723
Equity Method Investment, Summarized Financial Information, Assets		310,337	160,359	156,969
Equity Method Investment, Summarized Financial Information, Current Liabilities		54,710	30,131	34,736
Equity Method Investment, Summarized Financial Information, Long-term Liabilities	[1]	54,383	31,636	25,595
Equity Method Investment, Summarized Financial Information, Total Liabilities		109,093	61,767	60,331
Equity Method Investments Summarized Financial Information Net Assets		201,244	98,592	96,638
Other Affiliates [Member]
Investments In And Advances To Affiliates [Line Items]
Equity Method Investment, Summarized Financial Information, Assets		310,300
Equity Method Investments		$ 99,495	$ 38,469	$ 37,170

[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 investments in foreign affiliates associated with purchase of equipment and buildings.