Stockholders' Equity (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Dec. 14, 2011 New open market repurchase program [Member]	Mar. 31, 2012 Open Market Repurchase Program [Member]	Sep. 15, 2010 Open Market Repurchase Program [Member]
Stockholders' Equity (Textual) [Abstract]
Total capital stock, shares authorized	400,000,000
Common stock, shares authorized	300,000,000		300,000,000
Preferred stock, shares authorized	100,000,000		100,000,000
Common stock, par value per share	$ 0.01		$ 0.01
Maximum amount of dividends and or stock repurchases under credit facility	$ 50
Amount Available for Dividend Distribution for Restrictions on Dividends Stock and Notes Repurchases	80.4
Additional Stockholders' Equity (Textual) [Abstract]
Maximum Number of shares authorized for repurchase				4,000,000		4,000,000
Maximum amount of shares authorized under repurchase program				$ 100		$ 100
Condition to conclude repurchase program				Earliest of three years, when the maximum number of shares has been repurchased, or when the maximum dollar amount has been reached.
Number of shares repurchased and retired	0	0
Cumulative number of shares repurchased and retired					3,921,138
Cumulative weighted average price of repurchased and retired shares, per share					$ 25.39