Acquisitions, Divestiture, Intangible Assets and Goodwill (Goodwill) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Gross value before accumulated impairment					$ 1,742,427	$ 1,745,957
Accumulated impairment					(171,092)	0
Goodwill	$ 1,952,444	$ 1,571,335	$ 1,745,957	$ 1,745,957	1,571,335	1,745,957
Goodwill
Balance at		1,571,335	1,745,957
Acquisition		338,163	21,329
Impairment	(171,000)	0	(171,092)	0
Other		42,946	(24,859)
Balance at	1,952,444	1,952,444	1,571,335	1,745,957
North America Mailing
Goodwill [Line Items]
Gross value before accumulated impairment					354,000	357,215
Accumulated impairment					0	0
Goodwill	368,905	354,000	357,215	357,215	354,000	357,215
Goodwill
Balance at		354,000	357,215
Acquisition		0	0
Impairment		0	0
Other		14,905	(3,215)
Balance at	368,905	368,905	354,000	357,215
International Mailing
Goodwill [Line Items]
Gross value before accumulated impairment					145,566	148,351
Accumulated impairment					0	0
Goodwill	158,203	145,566	148,351	148,351	145,566	148,351
Goodwill
Balance at		145,566	148,351
Acquisition		0	0
Impairment		0	0
Other		12,637	(2,785)
Balance at	158,203	158,203	145,566	148,351
Production Mail
Goodwill [Line Items]
Gross value before accumulated impairment					101,099	105,757
Accumulated impairment					0	0
Goodwill	107,489	101,099	105,757	105,757	101,099	105,757
Goodwill
Balance at		101,099	105,757
Acquisition		0	0
Impairment		0	0
Other		6,390	(4,658)
Balance at	107,489	107,489	101,099	105,757
Presort Services
Goodwill [Line Items]
Gross value before accumulated impairment					196,890	196,890
Accumulated impairment					0	0
Goodwill	204,781	196,890	196,890	196,890	196,890	196,890
Goodwill
Balance at		196,890	196,890
Acquisition		7,891	0
Impairment		0	0
Other		0	0
Balance at	204,781	204,781	196,890	196,890
Software Solutions
Goodwill [Line Items]
Gross value before accumulated impairment					672,683	674,976
Accumulated impairment					(171,092)	0
Goodwill	510,605	501,591	674,976	674,976	501,591	674,976
Goodwill
Balance at		501,591	674,976
Acquisition		0	11,908
Impairment		0	(171,092)
Other		9,014	(14,201)
Balance at	510,605	510,605	501,591	674,976
Global Ecommerce
Goodwill [Line Items]
Gross value before accumulated impairment					272,189	262,768
Accumulated impairment					0	0
Goodwill	602,461	272,189	262,768	262,768	272,189	262,768
Goodwill
Balance at		272,189	262,768
Acquisition		330,272	9,421
Impairment		0	0
Other		0	0
Balance at	602,461	602,461	272,189	262,768
Small & Medium Business Solutions
Goodwill [Line Items]
Gross value before accumulated impairment					499,566	505,566
Accumulated impairment					0	0
Goodwill	527,108	499,566	505,566	505,566	499,566	505,566
Goodwill
Balance at		499,566	505,566
Acquisition		0	0
Impairment		0	0
Other		27,542	(6,000)
Balance at	527,108	527,108	499,566	505,566
Enterprise Business Solutions
Goodwill [Line Items]
Gross value before accumulated impairment					297,989	302,647
Accumulated impairment					0	0
Goodwill	312,270	297,989	302,647	302,647	297,989	302,647
Goodwill
Balance at		297,989	302,647
Acquisition		7,891	0
Impairment		0	0
Other		6,390	(4,658)
Balance at	312,270	312,270	297,989	302,647
Digital Commerce Solutions
Goodwill [Line Items]
Gross value before accumulated impairment					944,872	937,744
Accumulated impairment					(171,092)	0
Goodwill	1,113,066	773,780	937,744	937,744	$ 773,780	$ 937,744
Goodwill
Balance at		773,780	937,744
Acquisition		330,272	21,329
Impairment		0	(171,092)
Other		9,014	(14,201)
Balance at	$ 1,113,066	$ 1,113,066	$ 773,780	$ 937,744