Quarterly report pursuant to Section 13 or 15(d)

Long-term Debt - Additional Information (Details)

v3.19.1
Long-term Debt - Additional Information (Details)
3 Months Ended 12 Months Ended
Apr. 04, 2019
$ / shares
Mar. 31, 2019
USD ($)
$ / shares
Dec. 31, 2018
USD ($)
$ / shares
Sep. 30, 2018
$ / shares
Jun. 30, 2018
$ / shares
Mar. 31, 2018
USD ($)
$ / shares
Dec. 31, 2017
Debt Instrument [Line Items]              
Principal, net of issuance costs   $ 815,000,000 $ 835,000,000        
Dividends declared per share (in usd per share) | $ / shares   $ 0.335 $ 0.33 $ 0.33 $ 0.33 $ 0.33  
Total interest expense   $ 15,430,000       $ 18,711,000  
Convertible Senior Notes [Member] | 4.125% Convertible Senior Notes Due September 1, 2022 [Member]              
Debt Instrument [Line Items]              
Principal   150,000,000 $ 150,000,000        
Principal, net of issuance costs   $ 145,000,000          
Interest rate   4.125%          
Adjustment for dividends declared (in usd per share) | $ / shares   $ 0.335          
Redemption price, percentage             100.00%
Total interest expense   $ 2,000,000       $ 2,000,000  
Convertible Senior Notes [Member] | 4.125% Convertible Senior Notes Due September 1, 2022 [Member] | Subsequent Event [Member]              
Debt Instrument [Line Items]              
Conversion rate of shares for each $1,000 principal amount of convertible notes 36.7179            
Conversion price per share (in usd per share) | $ / shares $ 27.23