Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended							9 Months Ended		48 Months Ended
	Jun. 12, 2019	May 13, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Mar. 14, 2019	Aug. 31, 2017	Sep. 30, 2015
Class of Stock [Line Items]
Retirement of Series B preferred stock										$ 75,000	$ 0
Loss on retirement of preferred stock			$ 0	$ 1,956			$ 0			$ 1,956	$ 0
Quarterly dividend on all classes of common stock (in dollars per share)			$ 0.70	$ 0.70	$ 0.70	$ 0.58	$ 0.58	$ 0.58	$ 0.58
Series D Preferred Stock [Member]
Class of Stock [Line Items]
Issuance of stock (in shares)		4,000,000.0
Dividend rate		5.70%
Preferred stock, par value (in dollars per share)			25			25				$ 25		$ 25
Aggregate outstanding		$ 100,000
Issuance costs		$ 3,300
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Dividend rate	6.875%
Preferred stock, par value (in dollars per share)			$ 25			$ 25				$ 25		$ 25
Retirement of Series B preferred stock	$ 75,000
Loss on retirement of preferred stock	$ 2,000
Common Class C, Non-Voting [Member]
Class of Stock [Line Items]
Stock authorized for repurchase													$ 10,000	$ 5,400	$ 25,000
Shares repurchased (in shares)										0		668,000
Shares repurchased												$ 19,600