Stock Based Compensation Plans (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs related to non-vested	$ 2,300,000
Weighted-average period over which cost is expected to be recognized	2.3
Stock Based Compensation Plans (Textual) [Abstract]
Shares available for grant under the stock incentive plans	3,902,269
Weighted-average fair value for each option granted	$ 11.29	$ 5.45	$ 4.60
Period vested for restricted stock	3 years
Pay-out ranges, Minimum	0.00%
Pay-out ranges, Maximum	150.00%
Pay-out achievement	146.00%	150.00%	150.00%
Closing Price of Common Stock	30.11
Share pay-out at plan, net of forfeitures	14,563
Restricted stock and performance shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs related to non-vested	$ 9,900,000
Weighted-average period over which cost is expected to be recognized	1.7