Consolidated Balance Sheets Consolidated Balance Sheets (Parentheticals) - USD ($) shares in Thousands, $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Consolidated Balance Sheets Parentheticals [Abstract]
Allowance for Doubtful Accounts Receivable, Current	$ 1.5	$ 1.5
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	5,000	5,000
Preferred Stock, Shares Issued	0	0
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	395,000	395,000
Common Stock, Shares, Issued	90,689	90,689
Common Stock, Shares, Outstanding	82,151	83,303
Treasury Stock, Shares	8,538	7,386