Retirement and Compensation Plans Weighted average assumptions (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.65%				4.29%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	3.31%				3.31%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	4.52%	4.42%	4.05%	4.99%	4.65%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets	6.75%		7.00%		6.75%	7.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.31%		3.00%		3.31%	3.00%
Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage					0.55
Defined Benefit Plan, Actual Plan Asset Allocations					56.00%
Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage					0.40
Defined Benefit Plan, Actual Plan Asset Allocations					41.00%
Alternative investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage					0.05
Defined Benefit Plan, Actual Plan Asset Allocations					3.00%