Leases (Supplemental Cash Flow Information) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Leases [Abstract]
Cash paid for amounts included in the measurement of operating leases liabilities	$ 17,232	$ 14,619
Right-of-use assets obtained in exchange for operating lease obligations, net of early lease terminations	33,052	$ 17,064
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	106,962		$ 91,171
ezyVet
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	$ 7,900