Earnings Per Share Components of Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Weighted Average Number of Shares Outstanding, Basic and Diluted	89,160	89,003

Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

No definition available.

Name:	us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration