Employee Benefit Plans - Schedule of Weighted Average Actuarial Assumptions (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Sep. 30, 2017	Sep. 30, 2016
Pension
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.75%	4.57%	4.00%	3.88%
Rate of compensation increase	3.50%	3.50%	3.50%	3.50%
Discount rate	4.00%	3.75%	3.88%	4.50%
Expected rate of return on plan assets	7.25%	7.25%	7.50%	7.50%
Rate of compensation increase	3.50%	3.50%	3.50%	3.50%
RIM
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.63%	4.47%	3.88%	3.63%
Rate of compensation increase	3.50%	3.50%	3.50%	3.50%
Discount rate	3.88%	4.47%	3.63%	4.38%
Rate of compensation increase	3.50%	3.50%	3.50%	3.50%
Post-retirement
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.63%	4.41%	3.88%	3.63%
Discount rate	3.88%	3.63%	3.63%	4.38%