Stock Compensation Plans (Details Textual) (USD $)	12 Months Ended					1 Months Ended	12 Months Ended
	Dec. 31, 2011 1998 Long-Term Incentive Plan [Member]	Dec. 31, 2011 2006 Long-Term Incentive Plan [Member]	Dec. 31, 2009 2006 Long-Term Incentive Plan [Member]	Dec. 31, 2011 Prior To 2009 Long Term Incentive Plans [Member]	Dec. 31, 2010 2009 Long Term Incentive Plan [Member]	Feb. 28, 2011 2010 Long-Term Incentive Plan [Member]	Dec. 31, 2011 2010 Long-Term Incentive Plan [Member]
Stock Compensation Plans (Textual) [Abstract]
Number of shares reserved (in shares)	3,900,000	1,500,000					2,000,000
Period of vesting of awards	3 years	3 years
Period of life of awards granted	6 years	10 years		6 years	10 years		10 years
Percentage of shares vested initially (in hundredths)	40.00%
Period between former and latter vesting of options	2 years
Percentage of shares vested after two years (in hundredths)	20.00%
Vesting of exercisable options	10 years
Vesting of granted awards		3 years				3 years	3 years
Restricted stock awards, granted (in shares)			40,000			75,000
Restricted stock awards fair value, granted (in dollars per share)			$ 28.42			$ 30.66
Percentage of shares vested (in hundredths)		100.00%