Quarterly report pursuant to Section 13 or 15(d)

Convertible Senior Notes (Narrative) (Details)

v3.7.0.1
Convertible Senior Notes (Narrative) (Details)
1 Months Ended 6 Months Ended 12 Months Ended
Aug. 31, 2014
USD ($)
d
$ / shares
Jun. 30, 2017
USD ($)
Dec. 31, 2016
USD ($)
Debt Instrument [Line Items]      
Consecutive trading days     50 days
Equity component of currently redeemable convertible notes (Note 5)   $ 24,293,000 $ 29,563,000
2019 convertible senior notes      
Debt Instrument [Line Items]      
Aggregate principal amount outstanding   245,000,000 $ 245,000,000
Senior Notes | 2019 convertible senior notes      
Debt Instrument [Line Items]      
Interest rate (percent) 0.75%    
Aggregate principal amount outstanding $ 245,000,000.0    
Net proceeds from note after debt issuance costs $ 239,300,000    
Initial conversion rate 0.0133251    
Initial conversion price (in USD per share) | $ / shares $ 75.05    
If-converted value in excess of principal   $ 151,300,000  
Senior Notes | 2019 convertible senior notes | Debt Instrument, Redemption, Period One      
Debt Instrument [Line Items]      
Threshold trading days | d 20    
Consecutive trading days 30 days    
Percentage of stock price trigger to classify convertible debt as current 130.00% 130.00%  
Senior Notes | 2019 convertible senior notes | Debt Instrument, Redemption, Period Two      
Debt Instrument [Line Items]      
Threshold trading days | d 5    
Consecutive trading days 10 days    
Maximum threshold percentage of debt trading price trigger 98.00%