Stockholders' Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended					12 Months Ended
	Feb. 13, 2013	Nov. 01, 2012	Aug. 01, 2012	May 03, 2012	Feb. 15, 2012	Dec. 31, 2012
Class of Stock [Line Items]
Stock Repurchased						2,100,000
Aggregate cost for repurchase of common stock						$ 58.6
Shares surrendered to pay exercise price or satisfy tax withholding obligations for stock options exercised/restricted stock						55,879
Dividend amount to be paid, per common share	$ 0.2325	$ 0.225	$ 0.22	$ 0.215	$ 0.21
Dividend, declaration date	Feb. 12, 2013	Oct. 31, 2012	Jul. 31, 2012	May 02, 2012	Feb. 14, 2012
Dividend, date to be paid	Mar. 04, 2013	Nov. 26, 2012	Aug. 29, 2012	May 30, 2012	Mar. 12, 2012
Dividend, date of record	Feb. 25, 2013	Nov. 12, 2012	Aug. 13, 2012	May 16, 2012	Feb. 27, 2012
2012 Repurchase Program [Member]
Class of Stock [Line Items]
Maximum number of shares authorized to be repurchased						5,000,000