Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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

Earnings per Common Share Antidilutive Shares (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Performance Shares [Member]
Antidilutive Shares [Line Items]
Antidilutive shares			101	216
Common Class A [Member]
Antidilutive Shares [Line Items]
Antidilutive shares	134	480	101	289
Common Class A [Member] \| Stock Options [Member]
Antidilutive Shares [Line Items]
Antidilutive shares	0	56	0	73
Common Class A [Member] \| Performance Shares [Member]
Antidilutive Shares [Line Items]
Antidilutive shares	134	424