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Retirement Benefits - Schedule of Assumptions Used to Determine Periodic Benefit Expense (Income) (Details)
1 Months Ended 12 Months Ended
Dec. 01, 2015
Dec. 31, 2015
Dec. 31, 2016
Nov. 30, 2015
Nov. 30, 2014
Pension Benefits          
Defined Benefit Plan Disclosure [Line Items]          
Expected long-term rate of return on assets 7.00%   7.00% 8.00%  
Pension Benefits | Net Periodic Benefit Cost          
Defined Benefit Plan Disclosure [Line Items]          
Discount rate   4.26% 4.36% 3.96% 4.54%
Discount rate (non-qualified plan)   4.32% 4.41% 4.01% 4.65%
Expected long-term rate of return on assets   7.00%   8.00% 8.00%
Medical and Life Insurance Benefits          
Defined Benefit Plan Disclosure [Line Items]          
Ultimate healthcare trend rate     5.00%    
Initial healthcare trend rate (pre 65/post 65)     7.00%    
Medical and Life Insurance Benefits | Net Periodic Benefit Cost          
Defined Benefit Plan Disclosure [Line Items]          
Discount rate   3.87% 3.99% 3.54% 3.98%
Ultimate healthcare trend rate   5.00% 5.00% 5.00% 5.00%
Initial healthcare trend rate (pre 65/post 65)   7.00% 7.00% 7.00% 8.50%
Year ultimate rate attained (pre 65/post 65)   2021 2021 2021 2021