Share-Based Compensation Plans - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended	1 Months Ended			1 Months Ended	3 Months Ended
	Mar. 31, 2012	Jun. 30, 2012 CompensationPlan	Apr. 18, 2012 Plan Of 2012	Jun. 30, 2012 Plan Of 2012	Jun. 30, 2012 Directors Plan	Apr. 18, 2012 Employee Stock Purchase Plan	Mar. 31, 2012 Performance Restricted Stock Units	Mar. 31, 2012 Performance Restricted Stock Units Minimum	Mar. 31, 2012 Performance Restricted Stock Units Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of remaining shares that may be issued				5,656,338	49,099
Additional shares authorized			2,750,000			750,000
Reduction in the number of total shares for each stock option or stock appreciation rights granted, per share			1
Reduction in the number of total shares for each award of other share based awards, per share			2.87
Number of employee stock purchase programs		2
Total shareholder return risk-free interest rate	0.41%
Total shareholder return dividend yield	0.85%
Total shareholder return expected life in years	2 years 303 days
Awards requisite service period, in years							3 years
Percentage of target payout of employee varying from actual payout under award								0.00%	200.00%
Unrecognized compensation expenses related to share-based payment arrangements		$ 86.1
Weighted-average period of recognizing unrecognized compensation expenses related to share-based compensation, in years		3 years