Stock Options And Awards (Narrative) (Detail) (USD $)	1 Months Ended			12 Months Ended					1 Months Ended		12 Months Ended						12 Months Ended					12 Months Ended			12 Months Ended
	Oct. 28, 2012	Oct. 28, 2011	Oct. 28, 2010	Dec. 31, 2012 Company	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2011 Mr. J. Mike Walker's Stock Options [Member]	Dec. 31, 2010 Mr. Larry E. Reimert's Stock Options [Member]	Oct. 26, 2012 Restricted Stock Awards [Member]	May 10, 2012 Restricted Stock Awards [Member] Directors	Dec. 31, 2012 Restricted Stock Awards [Member]	Nov. 15, 2012 Restricted Stock Awards [Member]	Oct. 26, 2012 Restricted Stock Awards [Member] Employees [Member]	Oct. 26, 2012 Restricted Stock Awards [Member] Board Of Directors [Member]	May 10, 2012 Restricted Stock Awards [Member] Board Of Directors [Member]	Nov. 15, 2012 Restricted Stock Awards [Member] Newly Elected Director [Member]	Dec. 31, 2012 Non-Vested RSAs [Member]	Dec. 31, 2012 Performance Unit Awards [Member]	Oct. 26, 2012 Performance Unit Awards [Member]	Oct. 26, 2012 Performance Unit Awards [Member] Minimum [Member]	Oct. 26, 2012 Performance Unit Awards [Member] Maximum [Member]	Dec. 31, 2012 1997 Plan [Member]	Dec. 31, 2001 1997 Plan [Member]	Sep. 19, 1997 1997 Plan [Member]	Dec. 31, 2012 2004 Plan [Member]	May 13, 2004 2004 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of authorized shares purchased by options													84,250	4,800	4,800				46,350				1,400,000	3,400,000		2,696,294
Options granted period																						10 years			10 years
Options granted to employees, percentage of vesting per year																						25.00%			25.00%
Options granted	0	213,000	237,484
Intrinsic value of stock options exercised				$ 7,600,000	$ 4,900,000	$ 13,100,000
Income tax benefit realized from stock options exercised				2,700,000														82,000
Stock-based compensation expense for stock option exercises				3,800,000	4,500,000	5,000,000
Stock option expense for acceleration of the vesting stock							1,400,000	2,000,000
Allocated Share Based Compensation Expense Capitalized				0	0	0
Options granted to employees vesting period, in years				4 years
Unrecognized compensation expense related to nonvested stock options				7,200,000													8,600,000
Period of recognition for unrecognized compensation expense related to nonvested performance units				1 year 7 months 6 days													1 year 9 months	1 year 10 months 17 days
Vesting period of restricted shares issued under plans, years					3
Number of non employee directors received restricted stock awards										3
Closing price on the date of the grant									$ 69.55	$ 65.34		$ 67.56
Restricted stock units awarded to new directors																1,600
Grant date									Oct. 26, 2012
Restricted stock awards compensation expense				1,700,000	87,000	0
Total income tax benefit recognized in new income for restricted shares											460,000
Share value based on Monte Carlo simulation																			$ 84.66
Percentage of grant share price																		121.00%
Participants earning under the term																				0.00%	200.00%
Number of components companies in the Philadelphia Oil Service Index				15
Performance Unit compensation expense				235,000	0
Unrecognized compensation expense related to non-vested Performance Units				$ 3,700,000
Result rate based on which unrecognized compensation expense is considered				100.00%