Fair value measurements (acquisitions) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Acquisitions [Line Items]
Intangibles acquired		$ 139,212	$ 110,286	$ 54,575
2015 acquisitions [Member]
Acquisitions [Line Items]
Intangibles acquired		108,169
2015 acquisitions [Member] | Customer lists/relationships [Member]
Acquisitions [Line Items]
Intangibles acquired		101,867
2015 acquisitions [Member] | Internal-use software [Member]
Acquisitions [Line Items]
Intangibles acquired		4,902
2015 acquisitions [Member] | Software to be sold [Member]
Acquisitions [Line Items]
Intangibles acquired		$ 0
Verify Valid [Member]
Acquisitions [Line Items]
Contingent consideration, period		8 years
Liability for contingent consideration, maximum unlimited		There is no maximum amount of contingent payments specified in the agreement
Small business distributors [Member]
Acquisitions [Line Items]
Contingent consideration, period		3 years
Liability for contingent consideration, maximum amount		$ 925
2014 acquisitions [Member]
Acquisitions [Line Items]
Intangibles acquired	[1]		76,872
2014 acquisitions [Member] | Customer lists/relationships [Member]
Acquisitions [Line Items]
Intangibles acquired	[1]		45,022
2014 acquisitions [Member] | Internal-use software [Member]
Acquisitions [Line Items]
Intangibles acquired	[1]		1,300
2014 acquisitions [Member] | Software to be sold [Member]
Acquisitions [Line Items]
Intangibles acquired	[1]		28,500
Wausau Financial Systems, Inc. [Member]
Acquisitions [Line Items]
Deferred revenue acquired			$ 14,200
2013 acquisitions [Member]
Acquisitions [Line Items]
Intangibles acquired	[2]			53,975
2013 acquisitions [Member] | Customer lists/relationships [Member]
Acquisitions [Line Items]
Intangibles acquired	[2]			43,229
2013 acquisitions [Member] | Internal-use software [Member]
Acquisitions [Line Items]
Intangibles acquired	[2]			8,446
2013 acquisitions [Member] | Software to be sold [Member]
Acquisitions [Line Items]
Intangibles acquired	[2]			$ 0

[1] Includes adjustments recorded in 2015 for the finalization of purchase accounting for the Wausau acquisition. These adjustments decreased goodwill $714 from the preliminary amount recorded as of December 31, 2014, with the offset to certain income and sales tax accounts. The amount of intangible assets acquired includes assets classified as held for sale upon acquisition of $1,353.

[2] Includes adjustments recorded in 2014 for the finalization of purchase accounting for the Destination Rewards acquisition. These adjustments decreased goodwill $1,375 from the preliminary amount recorded as of December 31, 2013, with the offset to intangible assets. The amount of intangible assets acquired includes assets classified as held for sale upon acquisition of $24,502.