Debt (Narrative) (Details)												1 Months Ended	3 Months Ended			12 Months Ended
	Feb. 26, 2021 USD ($)	Feb. 18, 2021 USD ($)	Feb. 05, 2021 USD ($) quarter	Jan. 16, 2021 USD ($)	Feb. 25, 2020 USD ($)	Jan. 30, 2020 USD ($)	Jan. 21, 2020 USD ($)	Nov. 26, 2019 USD ($)	Apr. 15, 2019 USD ($) shares	Nov. 15, 2017 USD ($)	Apr. 30, 2014 shares	Jan. 31, 2017 shares	Sep. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Proceeds from credit agreement																$ 0	$ 0	$ 200,000,000
Amount expended on share repurchases in open market transactions																	288,483,000	453,853,000
Proceeds from issuance of senior long-term debt																$ 741,393,000	738,107,000	0
Contractual interest expense																		1,600,000
Amortization of debt issuance costs																		$ 8,100,000
Warrants exercised (in shares) | shares																		14,900,000
Shares issued upon exercise of warrants (in shares) | shares																		1,000,000
Warrants expired unexercised (in shares) | shares																		5,400,000
Warrants outstanding (in shares) | shares																		0
Unsecured Debt
Debt Instrument [Line Items]
Redemption price, as percentage of aggregate principal amount (percent)																101.00%
Line of Credit
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity								$ 250,000,000
Credit facility term								5 years
Potential increase in revolving credit facility commitment								$ 250,000,000
Amount outstanding																$ 0	$ 0
Line of Credit | Minimum
Debt Instrument [Line Items]
Quarterly facility fee (percent)																0.11%
Line of Credit | Maximum
Debt Instrument [Line Items]
Quarterly facility fee (percent)																0.20%
ASR Counterparty
Debt Instrument [Line Items]
Amount expended on share repurchases in open market transactions						$ 1,000,000,000
2026 Notes | Unsecured Debt
Debt Instrument [Line Items]
Debt instrument, face amount		$ 750,000,000														$ 750,000,000
Stated interest rate (percent)		1.25%
Proceeds from issuance of senior long-term debt		$ 741,400,000
2030 Notes | Unsecured Debt
Debt Instrument [Line Items]
Debt instrument, face amount					$ 750,000,000											750,000,000
Stated interest rate (percent)					3.30%
Proceeds from issuance of senior long-term debt					$ 738,100,000
2027 Notes | Unsecured Debt
Debt Instrument [Line Items]
Debt instrument, face amount										$ 750,000,000						$ 750,000,000
Stated interest rate (percent)										4.50%
Proceeds from issuance of senior long-term debt										$ 741,000,000
Senior Notes Due 2019
Debt Instrument [Line Items]
Stated interest rate (percent)									0.50%										0.50%
Convertible debt																			$ 1,440,000,000
Debt repaid									$ 1,160,000,000
Shares issued upon conversion of debt (in shares) | shares									4,900,000
Shares of common stock covered by note hedges (in shares) | shares											16,000,000
Additional warrant transaction (in shares) | shares											16,000,000
Adjustment to number of shares of common stock covered by Bond Hedges and Warrant Transactions (in shares) | shares												20,000,000
2021 Term Loan Credit Agreement
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 1,000,000,000		$ 1,000,000,000
Proceeds from credit agreement	$ 1,000,000,000
Consolidated leverage ratio (not more than)			4.0
Mandatory step-down consolidated leverage ratio after the fifth fiscal quarter ending after the date of the initial borrowing			3.75
Optional step-up consolidated leverage ratio			4.25
Number of fiscal quarters following a qualified acquisition | quarter			4
Consolidated interest coverage ratio (not less than)			3.0
2020 Credit Agreement
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity							$ 1,000,000,000
Proceeds from credit agreement						$ 1,000,000,000
Repayments of term loan credit agreement													$ 150,000,000		$ 750,000,000
2020 Credit Agreement | Unsecured 364-day Term Loan
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity							$ 500,000,000
Credit facility term					364 days		364 days
Repayments of term loan credit agreement					$ 500,000,000
2020 Credit Agreement | Unsecured 3-year Term Loan
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity							$ 500,000,000
Credit facility term					3 years		3 years
Repayments of term loan credit agreement					$ 250,000,000
Amended Term Loan Credit Agreement
Debt Instrument [Line Items]
Consolidated leverage ratio (not more than)			4.0
Mandatory step-down consolidated leverage ratio after the fifth fiscal quarter ending after the date of the initial borrowing			3.75
Optional step-up consolidated leverage ratio			4.25
Number of fiscal quarters following a qualified acquisition | quarter			4
Letter of Credit | Line of Credit
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity								25,000,000
Swing Line Loans | Line of Credit
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity								$ 10,000,000
Amended Credit Agreement
Debt Instrument [Line Items]
Consolidated leverage ratio (not more than)			4.0
Mandatory step-down consolidated leverage ratio after the fifth fiscal quarter ending after the date of the initial borrowing			3.75
Optional step-up consolidated leverage ratio			4.25
Number of fiscal quarters following a qualified acquisition | quarter			4
Credit Agreement | Unsecured 364-day Term Loan
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity				$ 1,450,000,000
Credit facility term				364 days
Debt issuance costs expensed														$ 5,400,000