Summary of Significant Accounting Policies (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accounting Policies [Abstract]
Authorized amount from board of directors for share repurchase	$ 250,000,000		$ 250,000,000
Shares repurchased under the program (in shares)	0	1,556,516	2,070,600	3,947,320
Cost of shares repurchased		$ 40,000,000	$ 34,700,000	$ 115,000,000