Quarterly report pursuant to Section 13 or 15(d)

Recent Accounting Pronouncements (Details)

v3.8.0.1
Recent Accounting Pronouncements (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2018
Jan. 01, 2018
Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]        
Retained earnings $ 2,560,719 $ 2,560,719   $ 2,568,764
Other current assets 1,797 1,797   2,797
Deferred income tax liabilities 939,821 939,821   932,593
Deferred revenue and other current liabilities 2,515 2,515   $ 5,168
Deferred revenue        
Deferred revenue current 1,900 1,900 $ 4,500  
Deferred revenue noncurrent 2,500 2,500 2,300  
Deferred revenue $ 4,400 4,400 6,800  
Revenue recognized   $ 2,600    
Revenue recognized percentage 85.00%      
Practical expedient modified contract   true    
ASU 2014-09 | Adjustment        
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]        
Retained earnings     1,200  
Other current assets     300  
Deferred income tax liabilities     400  
Deferred revenue and other current liabilities     $ (1,300)  
Minimum        
Deferred revenue        
Revenue recognized period 1 year      
Maximum        
Deferred revenue        
Revenue recognized period 3 years