Condensed Consolidated Statements of Stockholders' Equity (Parenthetical)	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
Stock issued for benefit plans (shares)	37,068	59,335
Stock options exercised (shares)	122,852	136,432
Public stock offering (shares)		4,038,270
Purchase of treasury shares (shares)	76,386	70,337
Employee stock purchase plan (shares)	49,089	66,564
Common Stock
Stock options exercised (shares)	122,852	136,432
Public stock offering (shares)		4,038,270
Employee stock purchase plan (shares)	49,089	66,564
Issuance of restricted stock (shares)	334,046	312,191
Additional Paid-in Capital
Stock issued for benefit plans (shares)	37,068	59,335
Stock options exercised (shares)	122,852	136,432
Public stock offering (shares)		4,038,270
Employee stock purchase plan (shares)	49,089	66,564
Issuance of restricted stock (shares)	334,046	312,191
Treasury Stock
Stock issued for benefit plans (shares)	37,068	59,335
Purchase of treasury shares (shares)	76,386	70,337