Equity - Narrative (Details) - USD ($)	3 Months Ended					42 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Mar. 31, 2019	Mar. 14, 2019	Aug. 31, 2017	Sep. 30, 2015
Class of Stock [Line Items]
Quarterly dividend on all classes of common stock (in dollars per share)	$ 0.7	$ 0.58	$ 0.58	$ 0.58	$ 0.58
Common Class C, Non-Voting [Member]
Class of Stock [Line Items]
Stock authorized for repurchase							$ 10,000,000	$ 5,400,000	$ 25,000,000
Shares repurchased (in shares)	0					668,000
Shares repurchased						$ 19,600,000