Merger Agreement - Additional Information (Detail) (USD $)	3 Months Ended
	Jun. 30, 2013	Jun. 12, 2013
Business Combinations [Abstract]
Cost of merger agreement		$ 2,500,000,000
Amount received by shareholders after acquisition agreement		$ 35.00
Amount over applicable exercise price of the option used as multiplier to calculate cash consideration for stock option		$ 35.00
Amount used as multiplier to calculate cash consideration for restricted stock units		$ 35.00
Amount used as multiplier to calculate cash consideration for performance stock units		$ 35.00
Number of reserved common shares held in treasury		1,906,183
Expenses related to merger agreement	$ 4,100,000