Fair Value Measurements - Narrative (Details)	3 Months Ended
	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated costs to sell foreclosed assets	6.00%
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustments for estimated costs to sell collateral dependent impaired loans	6.00%
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Adjustments for estimated costs to sell collateral dependent impaired loans	8.00%