Amortizable Intangible Assets - Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	$ 2,254,518	$ 2,200,061
Accumulated amortization	(1,209,519)	(1,150,401)
Net carrying value	1,044,999	1,049,660
Purchased Customer Accounts
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	2,218,554	2,164,968
Accumulated amortization	(1,176,833)	(1,118,316)
Net carrying value	$ 1,041,721	$ 1,046,652
Weighted average life (years)	15 years	15 years
Non-compete Agreements
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	$ 35,964	$ 35,093
Accumulated amortization	(32,686)	(32,085)
Net carrying value	$ 3,278	$ 3,008
Weighted average life (years)	4 years 4 months 24 days	4 years 7 months 6 days