Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2013

Share Repurchases [Abstract]

Schedule of Share Repurchases [Table Text Block]

Share repurchases were as follows:

	Years Ended December 31,
	2013		2012		2011
Shares repurchased in the open market	6,005,880		12,314,795		4,034,973
Shares repurchased from holders of employee stock options	5,951		86,303		80,166
Total shares repurchased	6,011,831		12,401,098		4,115,139
Average price paid per share	$	76.16	$	60.38	$	58.93