Summary of Significant Accounting Policies (Details Textual) - USD ($)	1 Months Ended		3 Months Ended			9 Months Ended
	Sep. 30, 2015		Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014	May. 31, 2015	Apr. 30, 2015	Dec. 31, 2014	Mar. 31, 2014
Accounting Policies [Abstract]
Authorized amount from board of directors for share repurchase												$ 250,000,000
Shares repurchased under the program (in shares)			1,556,516		407,100	3,947,320		747,246
Cost of shares repurchased			$ 40,000,000		$ 19,000,000	$ 115,000,000		$ 31,500,000
Shares repurchased settled in the subsequent month	$ 7,500,000
Common stock, shares authorized	400,000,000	[1]	400,000,000	[1]		400,000,000	[1]		400,000,000	200,000,000	200,000,000
Common Stock, Par Value (in dollars per share)	$ 0.01		$ 0.01			$ 0.01			$ 1.00	$ 0.01

[1] (unaudited)