Amortizable Intangible Assets - Amortizable Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 1,477,348	$ 1,428,426
Accumulated Amortization	(769,894)	(683,746)
Net Carrying Value	707,454	744,680
Purchased customer accounts
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	1,447,680	1,398,986
Accumulated Amortization	(741,770)	(656,799)
Net Carrying Value	$ 705,910	$ 742,187
Weighted Average Life (Years)	15 years	15 years
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 29,668	$ 29,440
Accumulated Amortization	(28,124)	(26,947)
Net Carrying Value	$ 1,544	$ 2,493
Weighted Average Life (Years)	6 years 9 months 18 days	6 years 9 months 18 days