Share Transactions - Share-Based Compensation (Details) (USD $)	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Stock Appreciation Rights And Options [Member]
Share-based compensation:
Share-based compensation, grants in period, shares	516,859	782,248
Weighted average grant date fair value of awards granted in period	$ 13.35	$ 9.91
Restricted Shares And Restricted Stock Units [Member]
Share-based compensation:
Share-based compensation, grants in period, shares	544,075	728,864
Weighted average grant date fair value of awards granted in period	$ 53.50	$ 38.59