Summary of Significant Accounting Policies (Details Textual)	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) shares	Jun. 30, 2015 USD ($) shares	Jun. 30, 2016 USD ($) customer shares	Jun. 30, 2015 USD ($) shares
Accounting Policies [Abstract]
Number of customers with outstanding accounts receivable greater than 10% | customer			1
Authorized amount from board of directors for share repurchase	$ 250,000,000		$ 250,000,000
Shares repurchased under the program (in shares) | shares	0	1,669,764	2,070,600	2,390,804
Cost of shares repurchased		$ 50,000,000	$ 34,700,000	$ 75,000,000
Percentage of consolidated outstanding accounts receivable made up by a customer with greater than 10%			11.00%