Shareholders' Equity (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 11, 2017	Dec. 31, 2016
Equity, Class of Treasury Stock [Line Items]
Common stock, authorized	1,200,000,000		1,200,000,000
Preferred shares, authorized	20,000,000		20,000,000
2017 Program [Member]
Equity, Class of Treasury Stock [Line Items]
Amount approved to repurchase, shares, maximum		$ 18,000