Consolidated Statements of Stockholders' Equity (Parenthetical) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Stockholders' Equity [Abstract]
Stock issued for benefit plans (shares)	352,476	154,665	104,890
Shares issued from stock option exercises	0	0	1,125
Purchase of treasury shares (shares)	70,437	102,673	98,020
Employee stock purchase plan (shares)	87,629	71,825	72,273
Issuance of restricted stock (shares)	304,166	392,292	391,581