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Stock Option Plan - Additional Information (Detail) (USD $)
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12 Months Ended | 1 Months Ended | 1 Months Ended | 1 Months Ended | 1 Months Ended | 1 Months Ended | 1 Months Ended | 1 Months Ended | 1 Months Ended | 1 Months Ended | 1 Months Ended | 1 Months Ended | 1 Months Ended | ||||||||||||||||||||||||||||||||||||||||||||||||
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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Apr. 26, 2004
2004 Options
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Apr. 26, 2004
2004 Options
Officer
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Apr. 26, 2004
2004 Options
Director
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May 06, 2005
2005 Options
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May 06, 2005
2005 Options
Officer
Person
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May 06, 2005
2005 Options
Director
Person
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May 01, 2006
2006 Options
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May 01, 2006
2006 Options
Director
Person
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Apr. 27, 2007
2007 Options
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Apr. 27, 2007
2007 Options
Officer
Person
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Apr. 27, 2007
2007 Options
Director
Person
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Apr. 25, 2008
2008 Options
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Apr. 25, 2008
2008 Options
Director
Person
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Apr. 24, 2009
2009 Options
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Apr. 24, 2009
2009 Options
Director
Person
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May 07, 2010
2010 Options
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May 07, 2010
2010 Options
Director
Person
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May 13, 2011
2011 Options
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May 13, 2011
2011 Options
Officer
Person
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May 13, 2011
2011 Options
Director
Person
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May 04, 2012
2012 Options
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May 04, 2012
2012 Options
Officer
Person
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May 04, 2012
2012 Options
Director
Person
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May 10, 2013
2013 Options
Person
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May 10, 2013
2013 Options
Officer
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May 10, 2013
2013 Options
Director
Person
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Dec. 31, 1993
Stock Options
the 1993 Plan
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Dec. 31, 2004
Stock Options
Amended 2004 Plan
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Dec. 31, 2004
Stock Options
Amended 2004 Plan
Director
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Apr. 26, 2004
Stock Options
2004 Options
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Apr. 26, 2004
Stock Options
2004 Options
Officer
Person
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Apr. 26, 2004
Stock Options
2004 Options
Director
Person
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May 06, 2005
Stock Options
2005 Options
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May 06, 2005
Stock Options
2005 Options
Officer
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May 01, 2006
Stock Options
2006 Options
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Apr. 27, 2007
Stock Options
2007 Options
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Apr. 27, 2007
Stock Options
2007 Options
Officer
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Apr. 25, 2008
Stock Options
2008 Options
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Apr. 24, 2009
Stock Options
2009 Options
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May 07, 2010
Stock Options
2010 Options
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May 13, 2011
Stock Options
2011 Options
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May 13, 2011
Stock Options
2011 Options
Officer
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May 04, 2012
Stock Options
2012 Options
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May 04, 2012
Stock Options
2012 Options
Officer
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May 10, 2013
Stock Options
2013 Options
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May 04, 2012
Stock Options
2013 Options
Officer
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Apr. 26, 2004
Incentive Stock Option
2004 Options
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May 06, 2005
Incentive Stock Option
2005 Options
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Apr. 27, 2007
Incentive Stock Option
2007 Options
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May 13, 2011
Incentive Stock Option
2011 Options
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May 04, 2012
Incentive Stock Option
2012 Options
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May 10, 2013
Incentive Stock Option
2013 Options
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Apr. 26, 2004
Nonqualified Stock Options
2004 Options
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May 06, 2005
Nonqualified Stock Options
2005 Options
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Apr. 27, 2007
Nonqualified Stock Options
2007 Options
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May 13, 2011
Nonqualified Stock Options
2011 Options
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May 04, 2012
Nonqualified Stock Options
2012 Options
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May 10, 2013
Nonqualified Stock Options
2013 Options
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| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Authorized shares for a grant | 400,000 | 2,000,000 | 200,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Options granted to purchase stocks (in shares) | 152,500 | 162,500 | 30,000 | 165,000 | 30,000 | 32,500 | 32,500 | 195,000 | 277,500 | 237,500 | 27,500 | 35,500 | 27,560 | 65,300 | 26,157 | 35,592 | 125,000 | 127,000 | 137,440 | 129,700 | 251,343 | 201,908 | |||||||||||||||||||||||||||||||||||||||
| Number of individuals granted options | 12 | 12 | 12 | 13 | 12 | 12 | 13 | 13 | 15 | 13 | 15 | 14 | 15 | 14 | 11 | 12 | |||||||||||||||||||||||||||||||||||||||||||||
| Plan expiration date | Apr. 25, 2014 | May 05, 2015 | Apr. 30, 2016 | Apr. 26, 2017 | Apr. 24, 2018 | Apr. 23, 2019 | May 06, 2020 | May 12, 2021 | May 03, 2022 | May 10, 2023 | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Options vested (in percent) | 25.00% | 25.00% | 25.00% | 25.00% | 25.00% | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Option vesting period | 4 years | 4 years | 4 years | 4 years | 4 years | 4 years | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Exercise price of options (in usd per share) | $ 44.42 | $ 39.29 | $ 41.82 | $ 25.78 | $ 33.22 | $ 40.35 | $ 54.17 | $ 50.15 | $ 32.68 | $ 38.76 | $ 41.82 | $ 39.29 | $ 44.42 | ||||||||||||||||||||||||||||||||||||||||||||||||
| Fair value stock option grant | $ 8,075,838 | $ 359,375 | $ 292,775 | $ 66,600 | $ 484,500 | $ 413,400 | $ 71,100 | $ 143,400 | $ 1,500,000 | $ 1,300,000 | $ 285,300 | $ 254,700 | $ 222,950 | $ 287,950 | $ 1,600,000 | $ 1,300,000 | $ 297,375 | $ 1,700,000 | $ 1,400,000 | $ 244,388 | $ 1,500,000 | $ 1,300,000 | $ 300,000 | ||||||||||||||||||||||||||||||||||||||
| Intrinsic value of options exercised | 600,000 | 1,600,000 | 700,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intrinsic value of options outstanding | 4,500,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intrinsic value of options exercisable | $ 2,800,000 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Closing share price | $ 47.73 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Weighted average remaining contractual life of the Company's exercisable options | 5 years 1 month 1 day | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Weighted average remaining contractual life of the Company's outstanding options | 6 years 9 months 4 days | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||