Amortizable Intangible Assets - Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	$ 2,241,676	$ 2,200,061
Accumulated amortization	(1,181,312)	(1,150,401)
Net carrying value	1,060,364	1,049,660
Purchased Customer Accounts
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	2,205,764	2,164,968
Accumulated amortization	(1,148,875)	(1,118,316)
Net carrying value	$ 1,056,889	$ 1,046,652
Weighted average life (years)	15 years	15 years
Non-compete Agreements
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	$ 35,912	$ 35,093
Accumulated amortization	(32,437)	(32,085)
Net carrying value	$ 3,475	$ 3,008
Weighted average life (years)	4 years 4 months 24 days	4 years 7 months 6 days