XML 82 R59.htm IDEA: XBRL DOCUMENT v3.8.0.1
Long-term debt (Details)
$ / shares in Units, $ in Millions
1 Months Ended 12 Months Ended
Nov. 14, 2017
USD ($)
shares
Aug. 12, 2016
shares
$ / shares
Dec. 11, 2013
Dec. 28, 2017
USD ($)
shares
Jan. 29, 2014
USD ($)
shares
$ / shares
Dec. 31, 2017
USD ($)
Institution
Long-Term Debt [Line Items]            
Interest rate percentage           2.875%
Debt instrument amortization period         7 years  
Letter of credit, outstanding amount           $ 1.0
Eurocurrency [Member]            
Long-Term Debt [Line Items]            
Debt instrument, basis spread on variable rate           1.00%
Eurocurrency [Member] | Minimum [Member]            
Long-Term Debt [Line Items]            
Debt instrument, basis spread on variable rate           1.50%
Eurocurrency [Member] | Maximum [Member]            
Long-Term Debt [Line Items]            
Debt instrument, basis spread on variable rate           2.50%
Base Rate [Member] | Minimum [Member]            
Long-Term Debt [Line Items]            
Debt instrument, basis spread on variable rate           0.50%
Base Rate [Member] | Maximum [Member]            
Long-Term Debt [Line Items]            
Debt instrument, basis spread on variable rate           1.50%
Federal Funds Rate [Member]            
Long-Term Debt [Line Items]            
Debt instrument, basis spread on variable rate           0.50%
Revolving Credit Facility [Member]            
Long-Term Debt [Line Items]            
Outstanding credit facility           $ 0.0
BAML Revolving Credit Facility [Member]            
Long-Term Debt [Line Items]            
Maturity date     Dec. 11, 2018      
Credit Agreement [Member]            
Long-Term Debt [Line Items]            
Maturity date           Sep. 29, 2022
Number of lending institutions | Institution           4
Current borrowing capacity           $ 200.0
Borrowing capacity with accordion feature           100.0
Maximum borrowing capacity           $ 300.0
Debt covenant, consolidated debt service coverage ratio, minimum           2.50
Debt covenant, leverage ratio, maximum           3.50
Credit Agreement [Member] | Minimum [Member]            
Long-Term Debt [Line Items]            
Commitment fee percentage           0.25%
Credit Agreement [Member] | Maximum [Member]            
Long-Term Debt [Line Items]            
Commitment fee percentage           0.40%
Debt covenant, leverage ratio, maximum           4.00
2.875% Convertible Senior Notes Due 2021 [Member]            
Long-Term Debt [Line Items]            
Face amount of debt instrument $ 250.0     $ 239.4 $ 250.0 $ 10.6
Interest rate percentage 2.875%       2.875%  
Maturity date         Jan. 15, 2021  
Conversion rate of notes per $1,000 principal amount (in shares) | shares 32.386 32.3860   8.5 30.8821  
Additional conversion rate of notes per $1,000 principal amount (in shares) | shares 3.1556          
Accrued interest on converted notes $ 2.4          
Conversion price per share (in dollars per share) | $ / shares   $ 30.88     $ 32.38  
Debt issuance costs       $ 3.6 $ 8.3