Benefit Plans (Effects of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates) (Details) - Postretirement Benefit Plan [Member]	12 Months Ended
	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Effect on total of service and interest cost, One-Percentage-Point Increase	8.00%
Effect on total of service and interest cost, One-Percentage-Point Decrease	(6.70%)
Effect on postretirement benefit obligation, One-Percentage-Point Increase	6.40%
Effect on postretirement benefit obligation, One-Percentage-Point Decrease	(5.40%)