Annual report pursuant to Section 13 and 15(d)

Basis of Presentation - Effects of Prior Period Errors Consolidated Statements of Changes in Shareholders' Equity (Detail)

v2.4.0.8
Basis of Presentation - Effects of Prior Period Errors Consolidated Statements of Changes in Shareholders' Equity (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2011
Sep. 30, 2011
Jun. 30, 2011
Mar. 31, 2011
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2012
Paid-in Capital in Excess of par Value [Member]
Dec. 31, 2011
Paid-in Capital in Excess of par Value [Member]
Dec. 31, 2010
Paid-in Capital in Excess of par Value [Member]
Dec. 31, 2012
Retained Earnings [Member]
Dec. 31, 2011
Retained Earnings [Member]
Dec. 31, 2010
Retained Earnings [Member]
Dec. 31, 2012
As Previously Reported [Member]
Sep. 30, 2012
As Previously Reported [Member]
Jun. 30, 2012
As Previously Reported [Member]
Mar. 31, 2012
As Previously Reported [Member]
Dec. 30, 2011
As Previously Reported [Member]
Sep. 30, 2011
As Previously Reported [Member]
Jun. 30, 2011
As Previously Reported [Member]
Mar. 31, 2011
As Previously Reported [Member]
Dec. 31, 2012
As Previously Reported [Member]
Dec. 31, 2011
As Previously Reported [Member]
Dec. 31, 2010
As Previously Reported [Member]
Dec. 31, 2012
As Previously Reported [Member]
Paid-in Capital in Excess of par Value [Member]
Dec. 31, 2011
As Previously Reported [Member]
Paid-in Capital in Excess of par Value [Member]
Dec. 31, 2010
As Previously Reported [Member]
Paid-in Capital in Excess of par Value [Member]
Dec. 31, 2012
As Previously Reported [Member]
Retained Earnings [Member]
Dec. 31, 2011
As Previously Reported [Member]
Retained Earnings [Member]
Dec. 31, 2010
As Previously Reported [Member]
Retained Earnings [Member]
Dec. 31, 2012
As Adjusted [Member]
Sep. 30, 2012
As Adjusted [Member]
Jun. 30, 2012
As Adjusted [Member]
Mar. 31, 2012
As Adjusted [Member]
Dec. 31, 2011
As Adjusted [Member]
Sep. 30, 2011
As Adjusted [Member]
Jun. 30, 2011
As Adjusted [Member]
Mar. 31, 2011
As Adjusted [Member]
Dec. 31, 2012
As Adjusted [Member]
Dec. 31, 2011
As Adjusted [Member]
Dec. 31, 2010
As Adjusted [Member]
Dec. 31, 2012
As Adjusted [Member]
Paid-in Capital in Excess of par Value [Member]
Dec. 31, 2011
As Adjusted [Member]
Paid-in Capital in Excess of par Value [Member]
Dec. 31, 2010
As Adjusted [Member]
Paid-in Capital in Excess of par Value [Member]
Dec. 31, 2012
As Adjusted [Member]
Retained Earnings [Member]
Dec. 31, 2011
As Adjusted [Member]
Retained Earnings [Member]
Dec. 31, 2010
As Adjusted [Member]
Retained Earnings [Member]
Condensed Financial Statements, Captions [Line Items]                                                                                                      
Beginning Balance       $ 548,144       $ 473,996 $ 548,144 $ 473,996 $ 351,218 $ 291,950 $ 249,902 $ 222,882 $ 293,887 $ 251,261 $ 151,612       $ 560,188       $ 487,212 $ 560,188 $ 487,212 $ 359,311 $ 291,950 $ 248,693 $ 222,882 $ 305,931 $ 265,686 $ 159,705       $ 548,144       $ 473,996 $ 548,144 $ 473,996 $ 351,218 $ 291,950 $ 249,902 $ 222,882 $ 293,887 $ 251,261 $ 151,612
Excess tax benefit from exercise of stock options, SARs and restricted stock grants                 29,684 26,241 9,254 29,684 26,241 9,254                         27,450 8,045    27,450 8,045                         26,241 9,254    26,241 9,254      
Net income 112,200 111,900 132,000 107,900 110,100 107,500 108,600 88,800 463,962 414,959 292,883       463,962 414,959 292,883 117,881 117,779 133,368 108,162 105,357 108,022 111,180 88,019 477,190 412,578 299,215       477,190 412,578 299,215 112,207 111,873 131,951 107,931 110,072 107,459 108,601 88,827 463,962 414,959 292,883       463,962 414,959 292,883
Ending Balance $ 395,483       $ 548,144       $ 395,483 $ 548,144 $ 473,996 $ 303,975 $ 291,950 $ 249,902 $ 123,096 $ 293,887 $ 251,261 $ 420,755               $ 420,755 $ 560,188 $ 487,212 $ 303,975 $ 291,950 $ 248,693 $ 148,368 $ 305,931 $ 265,686 $ 395,483       $ 548,144       $ 395,483 $ 548,144 $ 473,996 $ 303,975 $ 291,950 $ 249,902 $ 123,096 $ 293,887 $ 251,261