Share-Based Payments (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,400,000	$ 1,400,000	$ 3,453,000	$ 3,497,000
Total unrecognized stock-based compensation costs	$ 7,900,000		$ 7,900,000
Weighted average remaining contractual term for recognition of unrecognized stock-based compensation costs (in years)	2.4		2.4
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)			76,166
Weighted average grant date fair values per share of restricted stock (in dollars per share)			$ 33.74
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