New Accounting Pronouncements Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 133,405	$ 67,562
Restricted cash held in escrow for like-kind exchange	127,597	116,405
Escrow Deposit	11,799	9,660
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 272,801	$ 193,627	$ 566,310	$ 57,038