Amortizable Intangible Assets - Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	$ 2,060,934	$ 1,959,207
Accumulated amortization	(1,095,570)	(1,042,439)
Net carrying value	965,364	916,768
Purchased Customer Accounts
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	2,026,286	1,925,326
Accumulated amortization	(1,064,134)	(1,011,574)
Net carrying value	$ 962,152	$ 913,752
Weighted average life (years)	15 years	15 years
Non-compete Agreements
Finite-Lived Intangible Assets [Line Items]
Gross carrying value	$ 34,648	$ 33,881
Accumulated amortization	(31,436)	(30,865)
Net carrying value	$ 3,212	$ 3,016
Weighted average life (years)	4 years 7 months 6 days	4 years 7 months 6 days