Quarterly report pursuant to Section 13 or 15(d)

Borrowings (Senior secured revolving credit facility ) (Details)

v3.3.0.814
Borrowings (Senior secured revolving credit facility ) (Details) - USD ($)
$ in Thousands
 9 Months Ended
Sep. 30, 2015
Oct. 31, 2015
Dec. 31, 2014
Line of Credit Facility [Line Items]      
Senior secured revolving credit facility $ 99,000   $ 35,000
Senior Secured Revolving Credit Facility [Member]      
Line of Credit Facility [Line Items]      
Maximum borrowing capacity 500,000    
Current borrowing capacity $ 250,000    
Interest rate at period end (as a percent) 2.21%    
Unused capacity, commitment fee (as a percent) 0.50%    
Debt Instrument, Maturity Date Mar. 11, 2019    
Senior Secured Revolving Credit Facility [Member] | Subsequent Event [Member]      
Line of Credit Facility [Line Items]      
Current borrowing capacity   $ 300,000  
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%