Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Allowance for Doubtful Accounts Receivable, Current	$ 1,850	$ 2,628
Accumulated depreciation	570,720	444,842
Accumulated amortization	$ 81,613	$ 56,409
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0
Preferred Stock, Liquidation Preference, Value	$ 361,043	$ 0
Preferred Stock, Shares Authorized	4,000,000	0
Preferred Stock, Shares Issued	350,000	0
Common stock, $0.01 par value	$ 0.01	$ 0.01
Common stock shares authorized	190,000,000	100,000,000
Common stock shares issued	79,171,000	79,708,000
Treasury Stock, Common, Shares	106,000	1,024,000