Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Apr. 26, 2018	Dec. 31, 2016
Preferred Stock, Par or Stated Value Per Share	$ 100			$ 100
Treasury Stock, Shares, Acquired				84,400,000
Treasury Stock, Value, Acquired				$ 2.4
Payments for Repurchase of Common Stock	$ 800.0		$ 400.0
The 2016 Repurchase Program [Member]
Stock Repurchase Program, Authorized Amount						$ 4,000.0
The 2016 Repurchase Program [Member] | Open Market [Member]
Treasury Stock, Shares, Acquired	27,100,000
Treasury Stock, Value, Acquired	$ 814.3
The 2015 and 2016 Repurchase Program [Member] | Open Market [Member]
Treasury Stock, Shares, Acquired				50,100,000
Treasury Stock, Value, Acquired				$ 1,400.0
The 2017 ASR Agreement [Member]
Treasury Stock, Shares, Acquired	17,200,000	17,100,000
Payments for Repurchase of Common Stock	$ 500.0	$ 500.0
The 2018 Repurchase Program [Member] | Subsequent Event [Member]
Stock Repurchase Program, Authorized Amount					$ 2,000.0
Common Stock [Member]
Convertible Preferred Stock, Shares Issued upon Conversion	50,000
Series A Convertible Preferred Stock [Member] | Samsung Corning Precision Materials Co., Ltd. [Member]
Convertible Preferred Stock, Shares Issued upon Conversion	2,300