Employee Benefit Plans - Assumptions in Benefit Plans (Details) - Postretirement Benefits Other than Pensions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Weighted-average assumptions used to determine projected pension benefit obligations
Discount rate (as a percent)	4.25%	4.00%	4.75%
Health care cost trend rate for medical benefits assumed for next year (as a percent)	5.50%	6.00%	6.50%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) (as a percent)	4.50%	4.50%	4.50%
Year that the rate reaches the ultimate trend rate	2018	2018	2018
Discount rate beginning of year (as a percent)	4.00%	4.75%	4.00%