Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of income before income tax

Components of income before income taxes consist of the following:

	Year Ended December 31,
	2020		2019		2018
United States	$	2,442.3	$	2,011.2	$	2,151.7
Foreign	1,368.1		417.9		401.8
	$	3,810.4	$	2,429.1	$	2,553.5

Schedule of components of income tax expense

Components of income tax expense consist of the following:

	Year Ended December 31,
	2020		2019		2018
Current:
Federal	$	199.0	$	444.6	$	223.7
State	1.2		1.9		4.8
Foreign	21.4		(2.6)		20.6
Total current tax expense	221.6		443.9		249.1
Deferred:
Federal	109.0		(132.0)		687.6
State	(2.0)		(1.7)		(1.9)
Foreign	(31.4)		3.1		(825.7)
Total deferred tax (benefit) expense	75.6		(130.6)		(140.0)
	$	297.2	$	313.3	$	109.1

Schedule of effective income tax rate reconciliation

A reconciliation of the U.S. statutory income tax rate to the Company's effective income tax rate is as follows:

	Year Ended December 31,
	2020		2019		2018
U.S. federal statutory tax rate	21.0	%	21.0	%	21.0	%
Stock-based compensation	(7.6)		(2.5)		(2.5)
Income tax credits	(2.8)		(4.6)		(2.6)
Taxation of non-U.S. operations	(1.8)		(1.0)		(1.9)
Sale of non-inventory related assets between foreign subsidiaries	(0.8)		—		(6.3)
Foreign-derived intangible income deduction	—		(1.6)		(1.0)
Non-deductible Branded Prescription Drug Fee	0.5		0.7		0.6
Impact of change in U.S. corporate tax rate (the Act)	—		—		(2.7)
Other permanent differences	(0.7)		0.9		(0.3)
Effective income tax rate	7.8	%	12.9	%	4.3	%

Schedule of deferred tax assets and liabilities

Significant components of the Company's deferred tax assets and liabilities are as follows:

	As of December 31,
	2020		2019
Deferred tax assets:
Deferred compensation	$	436.6	$	519.7
Fixed assets and intangible assets	140.5		192.0
Accrued expenses	139.8		75.9
Deferred revenue	44.6		22.0
Total deferred tax assets	761.5		809.6
Valuation allowance	—		(7.0)
Deferred tax assets, net of valuation allowance	761.5		802.6
Deferred tax liabilities:
Other	(42.8)		(11.2)
Net deferred tax assets	$	718.7	$	791.4

Schedule of unrecognized tax benefits

The following table reconciles the beginning and ending amounts of unrecognized tax benefits. The amount of unrecognized tax benefits that, if settled, would impact the effective tax rate is $267.0 million, $210.8 million, and $189.5 million as of December 31, 2020, 2019, and 2018, respectively.

	2020		2019		2018
Balance as of January 1	$	210.8	$	189.5	$	146.2
Gross increases related to current year tax positions	76.6		37.9		51.4
Gross increases (decreases) related to prior year tax positions	7.2		(7.2)		5.6
Gross decreases due to settlements and lapse of statutes of limitations	(27.6)		(9.4)		(13.7)
Balance as of December 31	$	267.0	$	210.8	$	189.5