Quarterly report pursuant to Section 13 or 15(d)

Subsequent Events (Details)

v3.10.0.1
Subsequent Events (Details) - USD ($)
 3 Months Ended 6 Months Ended
Jul. 25, 2018
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Aug. 06, 2018
Subsequent Event [Line Items]            
Dividends declared per share (in dollars per share)   $ 0.750 $ 0.750 $ 1.500 $ 1.500  
Common Stock [Member] | Subsequent Event [Member]            
Subsequent Event [Line Items]            
Dividends declared per share (in dollars per share) $ 0.75          
Series A Cumulative Redeemable Preferred Stock [Member]            
Subsequent Event [Line Items]            
Coupon rate percentage       7.375%    
Series A Cumulative Redeemable Preferred Stock [Member] | Depositary Shares [Member] | Subsequent Event [Member]            
Subsequent Event [Line Items]            
Depositary stock, dividends declared per share (in dollars per share) $ 0.4609375          
Series A Cumulative Redeemable Preferred Stock [Member] | Preferred Stock [Member]            
Subsequent Event [Line Items]            
Coupon rate percentage       7.375%    
Forecast [Member]            
Subsequent Event [Line Items]            
Authorized repurchase amount           $ 10,000,000.0