Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts Receivable, Current	$ 2,628	$ 2,322
Accumulated depreciation	444,842	393,635
Accumulated amortization on other intangible assets	$ 56,409	$ 39,018
Preferred Stock, Par or Stated Value Per Share	$ 0.01
Preferred Stock, Shares Authorized	4,000,000
Preferred Stock, Shares Issued	0
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common stock shares authorized	100,000,000	100,000,000
Common stock shares issued	79,708,000	67,079,000
Treasury Stock, Common, Shares	1,024,000	980,000