Quarterly report pursuant to Section 13 or 15(d)

Borrowings (Senior secured revolving credit facility ) (Details)

v3.2.0.727
Borrowings (Senior secured revolving credit facility ) (Details) - USD ($)
$ in Thousands
6 Months Ended
Jun. 30, 2015
Dec. 31, 2014
Line of Credit Facility [Line Items]    
Senior secured revolving credit facility $ 75,000 $ 35,000
Senior Secured Revolving Credit Facility [Member]    
Line of Credit Facility [Line Items]    
Maximum borrowing capacity 500,000  
Current borrowing capacity 250,000  
Senior secured revolving credit facility $ 75,000 $ 35,000
Interest rate at period end (as a percent) 2.19%  
Unused capacity, commitment fee (as a percent) 0.50%  
Debt Instrument, Maturity Date Mar. 11, 2019  
Senior Secured Revolving Credit Facility [Member] | Minimum [Member]    
Line of Credit Facility [Line Items]    
Basis Spread on LIBOR (as a percent) 1.75%  
Senior Secured Revolving Credit Facility [Member] | Maximum [Member]    
Line of Credit Facility [Line Items]    
Basis Spread on LIBOR (as a percent) 2.75%