Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts Receivable, Allowance for Credit Loss, Current	$ 2,536	$ 2,244
Accumulated depreciation	692,081	607,903
Accumulated amortization	$ 114,775	$ 90,014
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Liquidation Preference, Value	$ 380,331	$ 367,360
Preferred Stock, Shares Authorized	4,000	4,000
Preferred Stock, Shares Issued	350	350
Common stock, $0.01 par value	$ 0.01	$ 0.01
Common stock shares authorized	190,000	190,000
Common stock shares issued	79,853	79,270
Treasury Stock, Common, Shares	271	126