Schedule Of Estimated Fair Value Of Option Using Black-Scholes Option Pricing Model, Weighted Average Assumptions (Detail) (USD $)
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3 Months Ended | 6 Months Ended | ||
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Jun. 30, 2013
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Jun. 30, 2012
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Jun. 30, 2013
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Jun. 30, 2012
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Stock Option
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Average risk free interest rate | 0.80% | 0.80% | 0.90% | 0.80% |
Average expected term (in years) | 4 years 4 months 24 days | 4 years 3 months 18 days | 4 years 7 months 6 days | 4 years 6 months |
Average expected volatility | 31.00% | 32.00% | 29.00% | 32.00% |
Weighted average fair value at grant date | $ 132.88 | $ 149.90 | $ 141.68 | $ 143.50 |
Employee Stock Purchase Plan
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Average risk free interest rate | 0.20% | 0.20% | ||
Average expected term (in years) | 0 years | 0 years | 1 year 3 months 18 days | 1 year 3 months 18 days |
Average expected volatility | 33.00% | 32.00% | ||
Weighted average fair value at grant date | $ 170.51 | $ 133.75 |