Equity (Details Textual) - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2016	Mar. 31, 2011
Class of Stock [Line Items]
Preferred stock, shares authorized	8,000
Payments for repurchase of common stock	$ 4,352.6	$ 1,365.4	$ 1,000.0
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
2018 Share Repurchase Program
Class of Stock [Line Items]
Authorized amount of share repurchases				$ 3,500.0
Repurchase of common stock, at cost, shares	4,300
Payments for repurchase of common stock	$ 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	3,300
Payments for repurchase of common stock	$ 3,000.0	$ 1,000.0	$ 1,000.0
2011 Share Repurchase Program
Class of Stock [Line Items]
Common stock shares authorized for repurchase						20,000
Repurchase of common stock, at cost, shares		1,200
Payments for repurchase of common stock		$ 365.4