Intangible Assets and Goodwill (Goodwill) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill
Balance at	$ 1,324,179	$ 1,324,179	$ 1,332,351
Acquisitions		8,463	(5,426)
Impairment		(198,169)	0	$ 0
FX Impact		17,812	(2,746)
Balance at		1,152,285	1,324,179	1,332,351
Commerce Services
Goodwill
Balance at	821,960	821,960	816,896
Acquisitions		8,463	5,064
Impairment		(198,169)
FX Impact		0	0
Balance at		632,254	821,960	816,896
Commerce Services | Global Ecommerce
Goodwill
Balance at	609,431	609,431	609,431
Acquisitions		0	0
Impairment	(198,000)	(198,169)
FX Impact		0	0
Balance at		411,262	609,431	609,431
Commerce Services | Presort Services
Goodwill
Balance at	212,529	212,529	207,465
Acquisitions		8,463	5,064
Impairment		0
FX Impact		0	0
Balance at		220,992	212,529	207,465
SendTech Solutions
Goodwill
Balance at	$ 502,219	502,219	515,455
Acquisitions		0	(10,490)
Impairment		0
FX Impact		17,812	(2,746)
Balance at		$ 520,031	$ 502,219	$ 515,455