Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018
Assets:
Marketable debt securities	$ 2,238.6	$ 2,970.3
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	1,974.1	2,541.1
Marketable equity securities	276.1	337.5
Derivative contracts	107.3	43.8
Plan assets for deferred compensation	24.5	27.7
Total	4,620.6	5,920.4
Liabilities:
Derivative contracts	3.7	8.3
Contingent consideration obligations	341.5	346.1	$ 346.1	$ 421.3	$ 409.8
Total	345.2	354.4
Fair Value, Measurements, Recurring | Corporate debt securities
Assets:
Marketable debt securities	1,353.5	1,695.1
Fair Value, Measurements, Recurring | Government securities
Assets:
Marketable debt securities	710.4	1,013.9
Fair Value, Measurements, Recurring | Mortgage and other asset backed securities
Assets:
Marketable debt securities	174.7	261.3
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	0.0	0.0
Marketable equity securities	276.1	7.9
Derivative contracts	0.0	0.0
Plan assets for deferred compensation	0.0	0.0
Total	276.1	7.9
Liabilities:
Derivative contracts	0.0	0.0
Contingent consideration obligations	0.0	0.0
Total	0.0	0.0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Corporate debt securities
Assets:
Marketable debt securities	0.0	0.0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Government securities
Assets:
Marketable debt securities	0.0	0.0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements, Recurring | Mortgage and other asset backed securities
Assets:
Marketable debt securities	0.0	0.0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	1,974.1	2,541.1
Marketable equity securities	0.0	329.6
Derivative contracts	107.3	43.8
Plan assets for deferred compensation	24.5	27.7
Total	4,344.5	5,912.5
Liabilities:
Derivative contracts	3.7	8.3
Contingent consideration obligations	0.0	0.0
Total	3.7	8.3
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate debt securities
Assets:
Marketable debt securities	1,353.5	1,695.1
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Government securities
Assets:
Marketable debt securities	710.4	1,013.9
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Mortgage and other asset backed securities
Assets:
Marketable debt securities	174.7	261.3
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	0.0	0.0
Marketable equity securities	0.0	0.0
Derivative contracts	0.0	0.0
Plan assets for deferred compensation	0.0	0.0
Total	0.0	0.0
Liabilities:
Derivative contracts	0.0	0.0
Contingent consideration obligations	341.5	346.1
Total	341.5	346.1
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Corporate debt securities
Assets:
Marketable debt securities	0.0	0.0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Government securities
Assets:
Marketable debt securities	0.0	0.0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Mortgage and other asset backed securities
Assets:
Marketable debt securities	$ 0.0	$ 0.0