Commitments and Contingencies - Narrative (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Rent expense	$ 25,200,000	$ 21,300,000	$ 20,300,000
Purchase price of receivable portfolios	2,894,900,000
Purchase price	400,800,000
Estimated fair value, liability	$ 0
Maximum
Loss Contingencies [Line Items]
Purchase commitment term	1 year