Employee Benefit Plans (Details 6)	1 Months Ended				12 Months Ended
	Sep. 30, 2013 USD ($)	Sep. 30, 2013 CHF	Sep. 30, 2012 USD ($)	Sep. 30, 2012 CHF	Mar. 31, 2014 USD ($)	Mar. 31, 2013 USD ($)	Mar. 31, 2014 Employee Stock Purchase Plans USD ($)	Mar. 31, 2013 Employee Stock Purchase Plans USD ($)	Mar. 31, 2012 Employee Stock Purchase Plans USD ($)	Mar. 31, 2014 Stock options and ESPP USD ($)	Mar. 31, 2013 Stock options and ESPP USD ($)	Mar. 31, 2013 Premium-priced stock options USD ($)	Mar. 31, 2013 Market-based Stock Options Plan USD ($)
Valuation Assumptions and Values
Dividend yield (as a percent)							0.43%	0.00%	0.00%		0.00%	0.00%	0.00%
Risk-free interest rate (as a percent)							0.07%	0.09%	0.13%		1.20%	2.00%	1.93%
Expected volatility (as a percent)							36.00%	47.00%	52.00%		46.00%	46.00%	44.00%
Expected life							6 months	6 months	6 months		6 years	7 years	6 years
Weighted average grant-date fair value (in dollars per share)							$ 2.46	$ 2.14	$ 2.96		$ 3.64	$ 2.52	$ 2.58
Additional disclosures
Dividends paid	$ 36,100,000	33,700,000	$ 133,500,000	125,700,000	$ 36,123,000	$ 133,462,000
Exercise price, lower range limit (in dollars per share)										$ 1
Exercise price, upper range limit (in dollars per share)										$ 35
Weighted average remaining contractual life of outstanding options										4 years 10 months 24 days
Weighted average remaining contractual life of exercisable options										3 years 7 months 6 days
Aggregate intrinsic value of outstanding options										20,100,000
Aggregate intrinsic value of exercisable options										$ 6,500,000
Total number of fully vested in-the-money options exercisable (in shares)										2,500,762
Unvested options (in shares)										2,756,753
Expected to vest (in shares)										2,370,808
Expected forfeitures (as a percent)										14.00%