Employee Benefit Plans - Narrative (Details)	3 Months Ended			9 Months Ended		12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($) entrant	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) entrant	Sep. 30, 2015 USD ($)	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of new entrants after pension plans were frozen | entrant		0		0
Employer contributions to the pension plans		$ 1,900,000	$ 0	$ 1,900,000.0	$ 0
Increase in pension liability				900,000
Settlement charge				1,200,000	900,000
Deferred actuarial loss				900,000
Accumulated benefits				2,700,000
Minimum | Forecast
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	$ (100,000)
Unrecognized actuarial losses						$ 16,000,000
Accumulated benefits						4,000,000
Maximum | Forecast
Defined Benefit Plan Disclosure [Line Items]
Settlement charge	$ (200,000)
Unrecognized actuarial losses						19,000,000
Accumulated benefits						$ 6,000,000
Other Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net period benefit costs			100,000	100,000	100,000
Expected employer contributions for current year				200,000
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net period benefit costs		$ 1,200,000	1,100,000	1,200,000	1,200,000
Settlement charge			$ 900,000	$ 1,200,000	$ 900,000