Employee Benefit Plans (Pension Plans' Range Targets) (Details)	Dec. 31, 2017
Equity Securities [Member]
Summary of target allocation percentage of assets
Target	25.00%
U.S. Equity [Member]
Summary of target allocation percentage of assets
Target	12.50%
International Equity [Member]
Summary of target allocation percentage of assets
Target	12.50%
Fixed Income, Money Market, Cash and Guaranteed Investment Contracts [Member]
Summary of target allocation percentage of assets
Target	75.00%
Fixed Income [Member]
Summary of target allocation percentage of assets
Target	73.00%
Money Market/Cash/Guaranteed Investments Contracts [Member]
Summary of target allocation percentage of assets
Target	2.00%