Benefit Plans - Schedule of Assumed Health Care Cost Trend Rates (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Health care cost trend rate assumed for the next year:
Pre-age 65 (as a percent)	7.25%	7.50%
Post-age 65 (as a percent)	7.00%	8.00%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	4.75%	4.75%