Income Taxes (Tables)

6 Months Ended

Sep. 30, 2018

Income Tax Disclosure [Abstract]

Summary of unrecognized tax benefits

The following tables summarize the activity related to the Company’s gross unrecognized tax benefits for the six months ended September 30, 2018 and the year ended March 31, 2018 (in millions):

	Six Months Ended September 30, 2018
Balance at March 31, 2018	$	436.0
Increases related to acquisitions	284.0
Decreases related to settlements with tax authorities	—
Decreases related to statute of limitation expirations	(11.3		)
Increases related to current year tax positions	23.2
Decreases related to prior year tax positions	(50.1		)
Balance at September 30, 2018	$	681.8

	Year Ended March 31, 2018
Balance at March 31, 2017	$	398.5
Increases related to acquisitions	—
Decreases related to settlements with tax authorities	(0.1		)
Decreases related to statute of limitation expirations	(10.9		)
Increases related to current year tax positions	30.3
Increases related to prior year tax positions	18.2
Balance at March 31, 2018	$	436.0