Equity - Antidilutive (Details) - shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Potentially dilutive shares
Excluded from EPS calculation (in shares)	15,893	17,008	21,139
Class B Common Stock
Potentially dilutive shares
Excluded from EPS calculation (in shares)	15,842	16,688	20,727
Stock options
Potentially dilutive shares
Excluded from EPS calculation (in shares)	13
Restricted stock
Potentially dilutive shares
Excluded from EPS calculation (in shares)	38	320	412

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/disclosureRef
-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