Segment Reporting (Revenue and Adjusted EBITDA for each Reportable Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net revenue	$ 866,065	$ 785,141	$ 2,560,684	$ 2,235,261
Adjusted EBITDA	259,539	233,424	788,728	662,119
Reconciliation of income (loss) before tax provision (benefit) to Adjusted EBITDA
Income (loss) before income tax provision (benefit)	(34,587)	(2,366)	(99,793)	(130,531)
Amortization of capitalized software developed for sale	935	460	2,510	550
Depreciation and amortization	170,782	151,143	502,463	436,552
Interest expense	58,433	61,439	177,284	185,733
Equity compensation	24,807	10,944	74,718	34,858
Acquisition accounting adjustments	(4,864)	20,601	(7,077)	103,826
Acquisition and divestiture-related costs	8,707	2,661	28,867	10,119
Integration and related costs	5,894	9,688	23,195	27,581
Strategic initiatives, duplicative and transition costs	13,492	4,324	38,064	13,169
Severance costs	2,640	2,591	14,663	10,467
Accretion and changes in estimate, net	4,482	(2,759)	13,570	8,429
Impairment of long-lived assets and other	2,537	658	4,230	14,418
Loss on extinguishment of debt	1,653	6,145	3,885	7,634
Gain on sale of businesses		(32,217)		(60,487)
Contingent consideration				(3,000)
Other non-routine, net	4,628	112	12,149	2,801
Adjusted EBITDA	259,539	233,424	788,728	662,119
Postage and Eliminations [Member]
Segment Reporting Information [Line Items]
Net revenue	20,322	22,006	56,431	73,142
Purchase Accounting Adjustment [Member]
Segment Reporting Information [Line Items]
Net revenue		(24,179)	(7,740)	(118,088)
Software and Analytics [Member]
Segment Reporting Information [Line Items]
Net revenue	386,020	372,212	1,169,760	1,118,661
Adjusted EBITDA	125,131	120,779	397,814	382,103
Reconciliation of income (loss) before tax provision (benefit) to Adjusted EBITDA
Adjusted EBITDA	125,131	120,779	397,814	382,103
Network Solutions [Member]
Segment Reporting Information [Line Items]
Net revenue	226,963	192,588	652,023	519,509
Adjusted EBITDA	120,735	103,847	343,208	268,858
Reconciliation of income (loss) before tax provision (benefit) to Adjusted EBITDA
Adjusted EBITDA	120,735	103,847	343,208	268,858
Technology-Enabled Services [Member]
Segment Reporting Information [Line Items]
Net revenue	232,760	222,514	690,210	642,037
Adjusted EBITDA	13,673	8,798	47,706	11,158
Reconciliation of income (loss) before tax provision (benefit) to Adjusted EBITDA
Adjusted EBITDA	13,673	8,798	47,706	11,158
Postage [Member]
Segment Reporting Information [Line Items]
Net revenue	$ 54,917	$ 49,877	$ 158,675	$ 145,672