Amortizable Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 1,030,636	$ 1,030,351
Accumulated Amortization	(479,947)	(463,813)
Net Carrying Value	550,689	566,538
Purchased customer accounts [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	1,005,316	1,005,031
Accumulated Amortization	(455,633)	(439,623)
Net Carrying Value	549,683	565,408
Weighted Average Life (years)	14 years 10 months 24 days	14 years 10 months 24 days
Non-compete agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	25,320	25,320
Accumulated Amortization	(24,314)	(24,190)
Net Carrying Value	$ 1,006	$ 1,130
Weighted Average Life (years)	7 years 2 months 12 days	7 years 2 months 12 days