Condensed Consolidated Balance Sheets (Parenthetical) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Allowance for receivables	$ 13,700,000		$ 13,000,000.0
Preferred Stock, Shares Authorized	2,357,299		2,357,299
Preferred Stock, 6 3/4% Cumulative Convertible, Shares Issued	155,250		155,250
Preferred Stock, 6 3/4% Cumulative Convertible, Shares Outstanding	155,250		155,250
Preferred Stock, Depositary Shares	3,105,000		3,105,000
Preferred Stock, Dividend Rate, Percentage	6.75%	6.75%
Preferred Stock, Liquidation Preference Per Share	$ 1,000		$ 1,000
Preferred Stock Liquidation Depositary Per Share	$ 50		$ 50
Common Stock, Par or Stated Value Per Share	$ 0.01		$ 0.01
Common Stock, Shares Authorized	96,000,000		96,000,000
Common Stock, Shares, Issued	50,420,449		50,184,114
Common Stock, Shares, Outstanding	50,420,449		50,184,114