Share Repurchases (Details) - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2016
Class of Stock [Line Items]
Preferred stock, shares authorized	8,000
Payments for repurchase of common stock	$ 5,868.3	$ 4,352.6	$ 1,365.4
Series A
Class of Stock [Line Items]
Preferred stock, shares authorized	1,750
Series X junior participating
Class of Stock [Line Items]
Preferred stock, shares authorized	1,000
Undesignated
Class of Stock [Line Items]
Preferred stock, shares authorized	5,250
December 2019 Share Repurchase Program [Member]
Class of Stock [Line Items]
Authorized amount of share repurchases	$ 5,000.0
March 2019 Share Repurchase Program
Class of Stock [Line Items]
Authorized amount of share repurchases				$ 5,000.0
Repurchase of common stock, at cost, shares	14,700
Payments for repurchase of common stock	$ 3,700.0
2018 Share Repurchase Program
Class of Stock [Line Items]
Authorized amount of share repurchases					$ 3,500.0
Repurchase of common stock, at cost, shares	8,900	4,300
Payments for repurchase of common stock	$ 2,100.0	$ 1,400.0
2016 Share Repurchase Program
Class of Stock [Line Items]
Authorized amount of share repurchases						$ 5,000.0
Repurchase of common stock, at cost, shares		10,500	3,700
Payments for repurchase of common stock		$ 3,000.0	$ 1,000.0