Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Schedule of Repurchase Agreements (Details)

v3.8.0.1
Stockholders' Equity - Schedule of Repurchase Agreements (Details) - USD ($)
shares in Thousands, $ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Shares Repurchase Activity [Line Items]      
Amount $ 1,403,283 $ 1,672,697 $ 2,015,947
Treasury stock value $ 17,154 $ 22,906  
Open Market      
Shares Repurchase Activity [Line Items]      
Shares (in shares) 270,527 420,111 524,222
Amount $ 1,403,283 $ 1,672,697 $ 2,015,947