Employee and Retiree Benefits (Narrative) (Details) - USD ($)	1 Months Ended					3 Months Ended	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012	Nov. 28, 2015	Dec. 31, 2016
Postretirement health care benefits age requirement before distribution occurs						55 years
Postretirement health care benefits continuous service requirement						15 years
Dollar cap liability reduction		10.00%	10.00%	10.00%	10.00%
Postretirement health care retiree age requirement						65 years
Subsequent Event [Member]
Dollar cap liability reduction	10.00%
Postretirement health care reimbursement account							$ 700,000