Share Repurchases (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2016
Class of Stock [Line Items]
Payments for repurchase of common stock			$ 3,057.3	$ 3,000.0
2019 Share Repurchase Program
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount					$ 5,000.0
Repurchase of common stock, at cost, shares			3.9
Payments for repurchase of common stock			$ 909.9
Amount remaining under 2019 Share Repurchase Program	$ 4,100.0		$ 4,100.0
2018 Share Repurchase Program
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount						$ 3,500.0
Repurchase of common stock, at cost, shares	6.5		8.9
Payments for repurchase of common stock	$ 1,500.0		$ 2,100.0
2016 Share Repurchase Program
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount							$ 5,000.0
Repurchase of common stock, at cost, shares		9.6		10.5
Payments for repurchase of common stock		$ 2,750.0		$ 3,000.0