Share-Based Payments (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,300,000	$ 1,600,000	$ 4,771,000	$ 5,060,000
Total unrecognized stock-based compensation costs	$ 6,900,000		$ 6,900,000
Weighted average remaining contractual term for recognition of unrecognized stock-based compensation costs (in years)	2.2		2.2
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted			146,581
Weighted average grant date fair value of each stock option granted (in dollars per option)			$ 6.47
Time Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)			76,966
Weighted average grant date fair values per share of restricted stock (in dollars per share)			$ 33.70
Total-Return Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)			57,386
Weighted average grant date fair values per share of restricted stock (in dollars per share)			$ 41.02