Annual report pursuant to Section 13 and 15(d)

Shareholders' Equity (Capital Stock) (Details)

v3.6.0.2
Shareholders' Equity (Capital Stock) (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
May 21, 2013
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
May 18, 2016
May 17, 2016
May 31, 2015
Nov. 21, 2014
Jun. 13, 2014
Dec. 31, 2013
Jun. 24, 2013
Class of Stock [Line Items]                      
Preferred stock, par value (in USD per share)   $ 0.0001 $ 0.0001                
Common stock, shares authorized (in shares)   1,000,000,000 800,000,000 800,000,000 1,000,000,000         600,000,000  
Preferred stock, shares authorized (in shares)   50,000,000 25,000,000   50,000,000 25,000,000          
At the market preferred stock, shares authorized (in shares)             12,000,000 12,000,000 12,000,000   12,000,000
Preferred stock, dividends, per share, cash paid, monthly (in USD per share)   $ 0.1667                  
Series A Preferred Stock                      
Class of Stock [Line Items]                      
Preferred stock, shares outstanding, designated (in shares) 5,290,000     6,000,000     3,000,000       3,000,000
Preferred stock, par value (in USD per share) $ 0.0001 $ 0.0001 $ 0.0001                
Preferred stock, shares authorized (in shares)   17,290,000 17,290,000                
Preferred stock, dividend rate 8.00% 8.00% 8.00%                
Preferred stock, liquidation preference (in USD per share) $ 25.00                    
Preferred stock, liquidation preference per month (in USD per share) $ 2.00                    
Redemption period 120 days                    
At the market shares sold (in shares)   1,161,895 3,586,790 4,906,734              
Proceeds from at the market preferred stock   $ 28,303 $ 86,352 $ 111,148              
Offering expenses   723 1,972 2,531              
Dividends paid   $ 30,438 $ 28,108 $ 17,244