Stockholders' Equity (Details Textuals) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended				6 Months Ended
	Mar. 31, 2010	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2015	Jun. 30, 2014
Percentage of shares outstanding at March 31, 2015			0.40%
Consideration issued	$ 3,000,000
Dividends declared per common share		$ 0.0625	$ 0.0625	$ 0.0625	$ 0.0625	$ 0.1250	$ 0.125
Annualized common stock cash dividend per share						$ 0.25	$ 0.25
Cash dividend payment						$ 43,528	$ 43,461
Treasury Stock, Shares, Acquired					12,400,000
Treasury Stock, Value, Acquired, Cost Method					$ 200,400
Adjustments for Error Correction
Decrease in number of shares		1,430,819
Share correction amount		$ 22,100				$ 22,100
Reduction in goodwill		22,100
Reduction in stockholders' equity		$ 22,100