Segment Reporting (Revenue and Adjusted EBITDA for each Reportable Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Net revenue	$ 867,856	$ 694,184
Adjusted EBITDA	282,728	196,856
Reconciliation of income (loss) before tax provision (benefit) to Adjusted EBITDA
Income (loss) before income tax provision (benefit)	(12,055)	(72,155)
Amortization of capitalized software developed for sale	717	78
Depreciation and amortization	168,211	138,541
Interest expense	59,386	62,667
Equity compensation	26,166	9,583
Acquisition accounting adjustments	(559)	48,540
Acquisition and divestiture-related costs	6,394	5,120
Integration and related costs	11,368	10,358
Strategic initiatives, duplicative and transition costs	9,928	5,080
Severance costs	4,720	4,704
Accretion and changes in estimate, net	4,732	5,895
Impairment of long-lived assets and other	1,612	6,313
Gain on sale of businesses		(28,095)
Contingent consideration		(2,450)
Other non-routine, net	2,108	2,677
Adjusted EBITDA	282,728	196,856
Postage and Eliminations [Member]
Segment Reporting Information [Line Items]
Net revenue	17,018	27,063
Purchase Accounting Adjustment [Member]
Segment Reporting Information [Line Items]
Net revenue	(4,461)	(55,000)
Software and Analytics [Member]
Segment Reporting Information [Line Items]
Net revenue	420,317	391,589
Adjusted EBITDA	160,365	143,932
Reconciliation of income (loss) before tax provision (benefit) to Adjusted EBITDA
Adjusted EBITDA	160,365	143,932
Network Solutions [Member]
Segment Reporting Information [Line Items]
Net revenue	209,461	142,826
Adjusted EBITDA	109,488	70,503
Reconciliation of income (loss) before tax provision (benefit) to Adjusted EBITDA
Adjusted EBITDA	109,488	70,503
Technology-Enabled Services [Member]
Segment Reporting Information [Line Items]
Net revenue	225,521	187,706
Adjusted EBITDA	12,875	(17,579)
Reconciliation of income (loss) before tax provision (benefit) to Adjusted EBITDA
Adjusted EBITDA	12,875	(17,579)
Postage [Member]
Segment Reporting Information [Line Items]
Net revenue	$ 51,208	$ 45,772