Employee Retirement Benefits - Assumptions Used for Periodic Income (Details) - Pension Benefits [Member]	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.35%	3.95%	4.80%
Salary increase	4.10%	4.10%	4.00%
Expected long-term rate of return	7.75%	7.75%	7.75%
Expected long-term rate of return, net of management fees	7.35%	7.35%