Earnings per share (Antidilutive) (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class A Common Stock
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Antidilutive shares excluded from the computation of diluted net earning per share	6,648	6,671	6,653
Class O units, TSR units, FFO units and options to purchase common stock on an "as if" converted basis
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Antidilutive shares excluded from the computation of diluted net earning per share	1,118	518	350
Series B Convertible preferred stock
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Antidilutive shares excluded from the computation of diluted net earning per share	6,778	6,729	3,484