Equity (Common Stock Changes In Number of Shares Issued, Held In Treasury and Outstanding) (Details) - shares		3 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Common Stock, Shares, Issued		79,137,758		79,137,758
Treasury Stock, Shares, Acquired		1,000,000
Common Stock Issuable [Member]
Class of Stock [Line Items]
Common Stock, Shares, Issued		79,137,758	79,137,758	79,137,758	79,137,758
Treasury Stock, Shares, Acquired		0
Stock Based Compensation Shares	[1]	0	0
Common Stock Held In Treasury [Member]
Class of Stock [Line Items]
Common Stock, Shares, Issued		15,465,272	14,645,901	14,685,663	14,835,256
Treasury Stock, Shares, Acquired		991,477
Stock Based Compensation Shares	[1]	(211,868)	(189,355)
Common Stock Outstanding [Member]
Class of Stock [Line Items]
Common Stock, Shares, Issued		63,672,486	64,491,857	64,452,095	64,302,502
Treasury Stock, Shares, Acquired		(991,477)
Stock Based Compensation Shares	[1]	(211,868)	(189,355)

[1] Represents net shares issued from treasury pursuant to the Company’s equity-based compensation programs.