Stock Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	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, 2012 Stock Incentive Plan	Mar. 31, 2012 Stock Incentive Plan	Sep. 30, 2012 Deferred Compensation Plan	Sep. 30, 2012 Deferred Compensation Plan	Sep. 30, 2012 Petrotech Incentive Plan [Member] Restricted Stock Units (RSUs) [Member] Vesting Period, Three Years [Member]	Sep. 30, 2012 Petrotech Incentive Plan [Member] Restricted Stock Units (RSUs) [Member] Vesting Period, Three Years [Member]	Sep. 30, 2012 Petrotech Incentive Plan [Member] Restricted Stock Units (RSUs) [Member] Vesting Period, Two Years [Member]	Sep. 30, 2012 Petrotech Incentive Plan [Member] Restricted Stock Units (RSUs) [Member] Vesting Period, Two Years [Member]	Sep. 30, 2012 Petrotech Incentive Plan [Member] Restricted Stock Units (RSUs) [Member] Vesting Period, 18 Months [Member]	Sep. 30, 2012 Petrotech Incentive Plan [Member] Restricted Stock Units (RSUs) [Member] Vesting Period, 18 Months [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Award Vesting Period	3 years					3 years		2 years		18 months
Award Expiration Period	10 years
Grants in Period, Options, Fair Value		$ 18.79
Grants in Period, Options		371,040
Grants in Period, Other than Options						102,349		3,768		40,822
Grants in Period, Other than Options, Fair Value					$ 51.17		$ 51.72		$ 51.99
Noncash Payments for Repurchase of Common Stock			$ 111	$ 229