Acquisitions, Intangible Assets and Goodwill (Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill before accumulated impairment					$ 1,548,107
Accumulated impairment					(148,181)
Goodwill	$ 1,774,645	$ 1,399,926	$ 1,399,926	$ 1,774,645	1,399,926
Goodwill
Balance at	1,774,645	1,399,926
Acquisitions	10,307	338,163
Impairment	0	0	148,181
Other	(18,441)	36,556
Balance at	1,766,511	1,774,645	1,399,926
Commerce Services
Goodwill [Line Items]
Goodwill before accumulated impairment				807,242	469,079
Accumulated impairment				0	0
Goodwill	807,242	469,079	469,079	807,242	469,079
Goodwill
Balance at	807,242	469,079
Acquisitions	10,307	338,163
Other	(653)	0
Balance at	816,896	807,242	469,079
Commerce Services | Global Ecommerce
Goodwill [Line Items]
Goodwill before accumulated impairment				602,461	272,189
Accumulated impairment				0	0
Goodwill	602,461	272,189	272,189	602,461	272,189
Goodwill
Balance at	602,461	272,189
Acquisitions	7,623	330,272
Other	(653)	0
Balance at	609,431	602,461	272,189
Commerce Services | Presort Services
Goodwill [Line Items]
Goodwill before accumulated impairment				204,781	196,890
Accumulated impairment				0	0
Goodwill	204,781	196,890	196,890	204,781	196,890
Goodwill
Balance at	204,781	196,890
Acquisitions	2,684	7,891
Other	0	0
Balance at	207,465	204,781	196,890
SMB Solutions
Goodwill [Line Items]
Goodwill before accumulated impairment				527,108	499,566
Accumulated impairment				0	0
Goodwill	527,108	499,566	499,566	527,108	499,566
Goodwill
Balance at	527,108	499,566
Acquisitions	0	0
Other	(11,653)	27,542
Balance at	515,455	527,108	499,566
SMB Solutions | North America Mailing
Goodwill [Line Items]
Goodwill before accumulated impairment				368,905	354,000
Accumulated impairment				0	0
Goodwill	368,905	354,000	354,000	368,905	354,000
Goodwill
Balance at	368,905	354,000
Acquisitions	0	0
Other	(657)	14,905
Balance at	368,248	368,905	354,000
SMB Solutions | International Mailing
Goodwill [Line Items]
Goodwill before accumulated impairment				158,203	145,566
Accumulated impairment				0	0
Goodwill	158,203	145,566	145,566	158,203	145,566
Goodwill
Balance at	158,203	145,566
Acquisitions	0	0
Other	(10,996)	12,637
Balance at	147,207	158,203	145,566
Software Solutions
Goodwill [Line Items]
Goodwill before accumulated impairment				588,476	579,462
Accumulated impairment				(148,181)	(148,181)
Goodwill	440,295	431,281	431,281	$ 440,295	$ 431,281
Goodwill
Balance at	440,295	431,281
Acquisitions	0	0
Other	(6,135)	9,014
Balance at	$ 434,160	$ 440,295	$ 431,281