Share-Based Compensation (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2010	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense	$ 1,100,000
Common shares available for the grant of stock options		1,933,604
Stock options grant expiry period, years		10
Aggregate intrinsic value of exercised options		3,500,000	1,900,000	2,000,000
Cash received from the exercise of options		5,532,000	3,459,000	4,171,000
Tax benefit realized from the exercise of options		1,400,000	800,000	800,000
Unrecorded deferred compensation cost of stock options, net of forfeitures		5,200,000
Weighted-average period to recognize unrecorded deferred compensation cost of stock options, years		1.93
Total fair value of nonvested stock		5,400,000	3,300,000	1,400,000
Accrued liabilities for cash-settled		3,100,000	2,900,000
Fair value per SAR		$ 10.85	$ 16.41
Nonvested Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecorded deferred compensation cost of stock options, net of forfeitures		11,600,000
Weighted-average period to recognize unrecorded deferred compensation cost of stock options, years		1.65
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payment to settle SARs exercised		600,000	100,000
Tax benefit realized from the exercise of options		200,000	100,000
Unrecorded deferred compensation cost of stock options, net of forfeitures		$ 1,600,000
Weighted-average period to recognize unrecorded deferred compensation cost of stock options, years		1.00