Dividends Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Dividends per Share [Abstract]
Cash dividend declared (in dollars per share)	$ 0.135	$ 0.20	$ 0.16
Payment of cash dividends		$ 48,374	$ 36,638	$ 31,189
Date dividend to be paid		Mar. 13, 2013
Date of record of stockholders to whom dividends will be paid		Feb. 22, 2013