Stockholders' Equity (Summary of Dividends Declared) (Details) (USD $) In Thousands, except Per Share data	6 Months Ended
	Jun. 30, 2011 Q1 2011 [Member]	Jun. 30, 2011 Q2 2011 [Member]	Jun. 30, 2010 Q1 2010 [Member]	Jun. 30, 2010 Q2 2010 [Member]
Declaration Date	Feb. 09, 2011	Apr. 27, 2011	Feb. 10, 2010	Apr. 27, 2010
Dividends per share	$ 0.07	$ 0.07	$ 0.07	$ 0.07
Record Date	Mar. 11, 2011	May 27, 2011	Mar. 11, 2010	May 27, 2010
Total Amount	$ 19,352	$ 19,232	$ 20,220	$ 19,902
Payment Date	Mar. 31, 2011	Jun. 17, 2011	Mar. 31, 2010	Jun. 17, 2010