Consolidated Statements of Stockholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock issued for benefit plans (shares)	37,068	59,335	94,023
Stock options exercised (shares)	130,902	136,432	26,056
Public Stock offering (shares)		4,038,270	6,210,000
Purchase of treasury shares (shares)	80,014	70,337	56,662
Employee stock purchase plan (shares)	49,089	66,564	50,690
Common Stock [Member]
Stock options exercised (shares)	130,902	136,432
Public Stock offering (shares)		4,038,270	6,210,000
Employee stock purchase plan (shares)	49,089	66,564	50,690
Issuance of restricted stock (shares)	348,972	312,191	263,908
Treasury Stock [Member]
Stock issued for benefit plans (shares)	37,068	59,335	94,023
Purchase of treasury shares (shares)	80,014	70,337	56,662
Additional Paid-in Capital [Member]
Stock issued for benefit plans (shares)	37,068	59,335	94,023
Stock options exercised (shares)	130,902	136,432	26,056
Public Stock offering (shares)		4,038,270	6,210,000
Employee stock purchase plan (shares)	49,089	66,564	50,690
Issuance of restricted stock (shares)	348,972	312,191	263,908