Annual report pursuant to Section 13 and 15(d)

Subsequent Events (Details)

v3.8.0.1
Subsequent Events (Details) - $ / shares
12 Months Ended
Jan. 24, 2018
Jan. 27, 2015
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Subsequent Event [Line Items]          
Dividends declared per share (in dollars per share)     $ 3.000 $ 3.000 $ 2.750
Common Stock [Member] | Subsequent Event [Member]          
Subsequent Event [Line Items]          
Dividends declared per share (in dollars per share) $ 0.750        
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% 7.375%