Share Transactions - Share-based compensation (Details) - $ / shares	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Stock appreciation rights and stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period, shares	492,466	427,379
Weighted average grant date fair value	$ 24.66	$ 17.46
Restricted shares and units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period, shares	511,636	456,217
Weighted average grant date fair value	$ 96.28	$ 71.61