Finance Receivable Sale Agreements - Master Purchase and Sale Agreement and Master Transfer Agreement (Details) - Consumer Loan - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended
	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2017
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Costs incurred related to purchase and sale agreement and master transfer agreement	$ 900,000
Purchase and Sale Agreement
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Transfer of financial assets, accounted for as sales, maximum amount eligible to be sold	375,000,000	$ 375,000,000	$ 375,000,000
Transfer of financial assets accounted for as sales, amount derecognized		241,300,000	241,300,000
Receivable purchase agreement, remaining unused capacity		112,400,000	112,400,000
Master Transfer Agreement
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Transfer of financial assets, accounted for as sales, maximum amount eligible to be sold	$ 292,200,000
Transfer of financial assets accounted for as sales, amount derecognized		106,600,000	106,600,000
Receivable purchase agreement, remaining unused capacity		177,100,000	177,100,000
Master Purchase and Sale Agreement and Master Transfer Agreement
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Gain on loan sales		$ 6,600,000	$ 15,000,000