Segment Information (Net (Loss) Income) (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Reconciliation of adjusted segment EBIT to net (loss) income:
Restructuring charges and asset impairments	$ (16,578)		$ (4,264)	$ (42,620)	$ (12,672)
Interest expense, net	(26,782)		(23,685)	(72,044)	(66,816)
Goodwill impairment	0		0	(118,599)	0
Gain (loss) on debt redemption/refinancing			0	3,064	(4,993)
Gain on sale of assets			0	0	14,372
Gain on sale of businesses, including transaction costs			8,398	0	10,920
Benefit (provision) for income taxes	4,185		(4,642)	16,850	(1,819)
Net (loss) income	(12,519)		5,487	(161,791)	30,644
Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBIT	85,173		80,914	254,337	271,016
Segment Reconciling Items
Reconciliation of adjusted segment EBIT to net (loss) income:
Unallocated corporate expenses	(41,704)		(42,908)	(145,762)	(141,537)
Restructuring charges and asset impairments	(16,578)		(4,264)	(42,620)	(12,672)
Interest expense, net	(43,595)		(37,377)	(118,156)	(104,643)
Proxy solicitation fees	0		0	(10,905)	0
Goodwill impairment	0		0	(118,599)	0
Gain (loss) on debt redemption/refinancing	0		0	3,064	(4,993)
Gain on sale of assets	0		0	0	14,372
Gain on sale of businesses, including transaction costs	0		13,764	0	10,920
Benefit (provision) for income taxes	4,185		(4,642)	16,850	(1,819)
Global Ecommerce
Segment Reporting Information [Line Items]
Adjusted EBIT	(41,712)		(34,881)	(114,033)	(77,402)
Reconciliation of adjusted segment EBIT to net (loss) income:
Goodwill impairment		$ (119,000)
Global Ecommerce | Operating Segments
Reconciliation of adjusted segment EBIT to net (loss) income:
Goodwill impairment				(118,599)
Presort Services
Segment Reporting Information [Line Items]
Adjusted EBIT	29,124		20,561	76,458	53,044
Presort Services | Operating Segments
Reconciliation of adjusted segment EBIT to net (loss) income:
Goodwill impairment				0
SendTech Solutions
Segment Reporting Information [Line Items]
Adjusted EBIT	$ 97,761		$ 95,234	291,912	$ 295,374
SendTech Solutions | Operating Segments
Reconciliation of adjusted segment EBIT to net (loss) income:
Goodwill impairment				$ 0