Stock Compensation Plans (Details 4) (USD $)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Summary of nonvested stock compensation awards
Number of nonvested shares outstanding, beginning balance	659,309	634,976	720,692	677,111
Weighted average grant date fair value nonvested shares, beginning balance	$ 9.80	$ 7.87	$ 7.46	$ 8.81
Number of nonvested shares outstanding, granted	379,425	390,750	372,750
Weighted average grant date fair value nonvested shares, granted	$ 11.42	$ 8.62	$ 5.97
Number of nonvested shares outstanding, vested	(311,630)	(453,744)	(322,003)
Weighted average grant date fair value nonvested shares, vested	$ 7.80	$ 8.50	$ 8.57
Number of nonvested shares outstanding, forfeited	(43,462)	(22,722)	(7,166)
Weighted average grant date fair value nonvested shares, forfeited	$ 9.77	$ 7.59	$ 8.10
Number of nonvested shares outstanding, ending balance	659,309	634,976	720,692	677,111
Weighted average grant date fair value nonvested shares, ending balance	$ 9.80	$ 7.87	$ 7.46	$ 8.81