Tangible Equity Units (Settlement conditions) (Details)	Sep. 30, 2018 $ / shares
Condition One
Tangible Equity Units [Line Items]
Share price (usd per share)	$ 159.54
Condition One | Minimum
Tangible Equity Units [Line Items]
Tangible Equity Rate, Settlement Rate	0.3134
Condition Two
Tangible Equity Units [Line Items]
Tangible Equity Units, Conditional Value	50
Condition Two | Minimum
Tangible Equity Units [Line Items]
Share price (usd per share)	130.25
Condition Two | Maximum
Tangible Equity Units [Line Items]
Share price (usd per share)	159.54
Condition Three
Tangible Equity Units [Line Items]
Share price (usd per share)	130.25
Condition Three | Maximum
Tangible Equity Units [Line Items]
Tangible Equity Rate, Settlement Rate	$ 0.3839