Condensed Consolidated Statements of Stockholders' Equity (Parenthetical)	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Dec. 31, 2010
Stock issued for benefit plans (shares)	37,068	59,335
Stock options exercised (shares)	128,502	136,432
Public stock offering (shares)		4,038,270
Purchase of treasury shares (shares)	77,362	70,337
Employee stock purchase plan (shares)	49,089	66,564
Common Stock [Member]
Stock options exercised (shares)	128,502	136,432
Public stock offering (shares)		4,038,270
Employee stock purchase plan (shares)	49,089	66,564
Issuance of restricted stock (shares)	337,556	312,191
Treasury Stock [Member]
Stock issued for benefit plans (shares)	37,068	59,335
Purchase of treasury shares (shares)	77,362	70,337