Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidated Statements of Changes in Stockholders' Equity
Issuance of common stock for stock options, shares			111,792
Issuance of common stock for restricted share awards, shares	1,029,623	670,933	787,399
Issuance of common stock for employee stock unit awards, shares		71,580	288,917
Issuance of common stock for restricted share awards, tax benefit shortfall and award cancellations (in dollars)	$ 1.5	$ 4.1	$ 3.3
Awards reclassified to liability for cash settlement, shares		259,840
Issuance of common stock for the employee stock purchase plan, shares	121,363	137,782	108,621
Purchase of common stock for treasury, shares	2,005,200	2,470,000	2,974,200
Shares withheld for net settlements of share-based awards, shares	352,051	270,467	369,099