Stockholders' Equity - Repurchase Program (Details)			2 Months Ended	3 Months Ended						9 Months Ended			12 Months Ended	36 Months Ended	44 Months Ended
	Jan. 29, 2019 shares	Dec. 14, 2018 USD ($) $ / shares shares	Jan. 29, 2019 $ / shares	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2019 USD ($)		Sep. 30, 2018 USD ($)	Dec. 31, 2018 transaction	Jan. 22, 2019 USD ($)	Sep. 30, 2019 USD ($) shares	Oct. 22, 2019 USD ($)
Class of Stock [Line Items]
Shares repurchased (in shares) | shares	117,751	1,057,035
Shares repurchased				$ 58,336,000	$ 702,000	$ 3,322,000	$ 0	$ 292,359,000	$ 88,292,000
Repurchase of common stock										$ 59,362,000	[1]	$ 380,651,000
Initial price paid (in dollars per share) | $ / shares		$ 176.91
Final price paid (in dollars per share) | $ / shares			$ 187.27
Number of transactions | transaction													2
Common Stock
Class of Stock [Line Items]
Stock repurchase program, approved amount				3,100,000,000						3,100,000,000					$ 3,100,000,000
Remaining authorized repurchase amount				$ 1,500,000,000						$ 1,500,000,000					$ 1,500,000,000
Repurchase agreements
Class of Stock [Line Items]
Shares repurchased (in shares) | shares															9,238,760
Shares repurchased														$ 1,600,000,000
Repurchase of common stock		$ 220,000,000
Repurchase agreements | Common Stock
Class of Stock [Line Items]
Stock repurchase program, approved amount		$ 220,000,000
Subsequent Event | Common Stock
Class of Stock [Line Items]
Increase in authorized amount to be repurchased																$ 1,000,000,000

[1] Reflects the impact of the Company's adoption of ASU 2016-02 "Leases", on January 1, 2019, using the modified retrospective transition method. Under this method, financial results reported in periods prior to 2019 are unchanged. Refer to footnote 2.