Stock Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended	1 Months Ended	3 Months Ended						9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2013 Stock options	Sep. 30, 2013 Stock options	Jan. 31, 2013 Restricted Stock	Sep. 30, 2013 Restricted Stock	Sep. 30, 2013 Performance share awards 2 year vesting period	Sep. 30, 2013 Performance share awards 3 year vesting period	Sep. 30, 2013 Performance share awards Petrotech Incentive Plan 3 year vesting period	Sep. 30, 2013 Stock Appreciation Rights (SARs)	Mar. 31, 2013 Restricted Stock Units (RSUs) Petrotech Incentive Plan	Sep. 30, 2013 Restricted Stock Units (RSUs) Petrotech Incentive Plan	Sep. 30, 2013 Restricted Stock Units (RSUs) Petrotech Incentive Plan 3 year vesting period	Sep. 30, 2013 Restricted Stock Units (RSUs) Petrotech Incentive Plan 3 year vesting period	Sep. 30, 2013 Restricted Stock Units (RSUs) Petrotech Incentive Plan 17 month vesting period	Sep. 30, 2013 Restricted Stock Units (RSUs) Petrotech Incentive Plan 17 month vesting period	Sep. 30, 2013 Deferred Compensation	Sep. 30, 2013 Deferred Compensation
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period		3 years		3 years	2 years	3 years	3 years	3 years				3 years		17 months
Expiration period	10 years
Grants in period, options		134,076
Grants in period, options, fair value		$ 16.66
Grants in period (in shares)			46,121		84,311	80,395	52,768	88,000	33,796		5,854		2,952
Grants in period, fair value (in dollars per share)			$ 48.36		$ 59.19	$ 60.81	$ 133.58	$ 39.10		$ 75.67				$ 75.88
Noncash payments for repurchase of common stock															$ 0.8	$ 0.9