Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of options outstanding.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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Stock-Based Compensation Plans (Details 2) (USD $)	12 Months Ended
Stock-Based Compensation Plans (Details 2) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Options
Stock-Based Compensation Plans
Intrinsic value of options exercised	$ 26,746,000	$ 46,126,000	$ 30,811,000
2009 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	307,554
Options outstanding intrinsic value	7,049,000
Options exercisable intrinsic value	2,845,000
Options exercisable weighted average contractual life	8 years 3 months 18 days
1994 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	719,830
Options outstanding intrinsic value	21,730,000
Options exercisable intrinsic value	$ 21,730,000
Options exercisable weighted average contractual life	4 years 1 month 6 days
30.00 - 39.99 \| 1994 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	1,424
Exercise Price (Lower range of limit)	$ 30.00
Exercise Price, upper limit (in dollars per share)	$ 39.99
Weighted Average Remaining Contractual Term	1 month 6 days
40.00 - 49.99 \| 1994 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	94,898
Exercise Price (Lower range of limit)	$ 40.00
Exercise Price, upper limit (in dollars per share)	$ 49.99
Weighted Average Remaining Contractual Term	3 years 6 months
60.00 - 69.99 \| 1994 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	41,556
Exercise Price (Lower range of limit)	$ 60.00
Exercise Price, upper limit (in dollars per share)	$ 69.99
Weighted Average Remaining Contractual Term	2 years 1 month 6 days
70.00 - 79.99 \| 2009 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	69,287
Exercise Price (Lower range of limit)	$ 70.00
Exercise Price, upper limit (in dollars per share)	$ 79.99
Weighted Average Remaining Contractual Term	7 years 1 month 6 days
70.00 - 79.99 \| 1994 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	730
Exercise Price (Lower range of limit)	$ 70.00
Exercise Price, upper limit (in dollars per share)	$ 79.99
Weighted Average Remaining Contractual Term	2 years 6 months
80.00 - 89.99 \| 1994 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	107,833
Exercise Price (Lower range of limit)	$ 80.00
Exercise Price, upper limit (in dollars per share)	$ 89.99
Weighted Average Remaining Contractual Term	5 years 1 month 6 days
90.00 - 99.99 \| 1994 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	187,380
Exercise Price (Lower range of limit)	$ 90.00
Exercise Price, upper limit (in dollars per share)	$ 99.99
Weighted Average Remaining Contractual Term	3 years 1 month 6 days
110.00 - 119.99 \| 2009 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	127,930
Exercise Price (Lower range of limit)	$ 110.00
Exercise Price, upper limit (in dollars per share)	$ 119.99
Weighted Average Remaining Contractual Term	8 years 1 month 6 days
130.00 - 139.99 \| 2009 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	108,838
Exercise Price (Lower range of limit)	$ 130.00
Exercise Price, upper limit (in dollars per share)	$ 139.99
Weighted Average Remaining Contractual Term	9 years 6 months
140.00 - 149.99 \| 2009 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	1,499
Exercise Price (Lower range of limit)	$ 140.00
Exercise Price, upper limit (in dollars per share)	$ 149.99
Weighted Average Remaining Contractual Term	9 years 1 month 6 days
140.00 - 149.99 \| 1994 Plan
Stock-Based Compensation Plans
Number of Options (in shares)	286,009
Exercise Price (Lower range of limit)	$ 140.00
Exercise Price, upper limit (in dollars per share)	$ 149.99
Weighted Average Remaining Contractual Term	4 years 1 month 6 days