Segment Information (Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenue	$ 1,049,117	$ 842,820	$ 821,371	$ 836,640	$ 887,069	$ 839,031	$ 835,886	$ 844,589	$ 3,549,948	$ 3,406,575	$ 3,578,060
United States
Segment Reporting Information [Line Items]
Revenue									2,738,711	2,589,535	2,681,285
Outside United States
Segment Reporting Information [Line Items]
Revenue									811,237	817,040	896,775
Small & Medium Business Solutions
Segment Reporting Information [Line Items]
Revenue									1,740,231	1,838,736	1,979,888
Small & Medium Business Solutions | North America Mailing
Segment Reporting Information [Line Items]
Revenue									1,356,561	1,427,094	1,530,060
Small & Medium Business Solutions | International Mailing
Segment Reporting Information [Line Items]
Revenue									383,670	411,642	449,828
Enterprise Business Solutions
Segment Reporting Information [Line Items]
Revenue									905,095	880,285	894,790
Enterprise Business Solutions | Production Mail
Segment Reporting Information [Line Items]
Revenue									407,194	404,703	421,178
Enterprise Business Solutions | Presort Services
Segment Reporting Information [Line Items]
Revenue									497,901	475,582	473,612
Digital Commerce Solutions
Segment Reporting Information [Line Items]
Revenue									904,622	687,554	648,575
Digital Commerce Solutions | Software Solutions
Segment Reporting Information [Line Items]
Revenue									352,380	348,234	385,908
Digital Commerce Solutions | Global Ecommerce
Segment Reporting Information [Line Items]
Revenue									552,242	339,320	262,667
Other
Segment Reporting Information [Line Items]
Revenue									$ 0	$ 0	$ 54,807