Commitments and Contingencies - Additional Information (Details) customer in Millions, $ in Billions		1 Months Ended
	Jan. 18, 2018	Apr. 30, 2018	Sep. 30, 2018 USD ($)	Mar. 16, 2018 plantiff	Dec. 31, 2017 USD ($)	Dec. 01, 2017 customer
Commitments and Contingencies Disclosure [Abstract]
Unused credit available to accountholders | $			$ 1.6		$ 26.4
Loss Contingencies [Line Items]
Number of days to file amended complaint	30 days
Number of customers with potentially compromised information | customer						1.6
Number of new court appointed plaintiffs | plantiff				2
Minimum
Loss Contingencies [Line Items]
Number of days to file amended complaint		30 days
Maximum
Loss Contingencies [Line Items]
Number of days to file amended complaint		3 years