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Earnings Per Share and Dividends - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 3 Months Ended 9 Months Ended
Oct. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Sep. 30, 2019
Sep. 30, 2018
Dividends Payable [Line Items]                  
Dividends declared and paid   $ 3,745 $ 3,739 $ 3,740 $ 3,549 $ 3,549 $ 3,547 $ 11,224 $ 10,645
Common Class A                  
Dividends Payable [Line Items]                  
Cash dividends declared per share of Class A common stock   $ 0.21 $ 0.21 $ 0.21 $ 0.20 $ 0.20 $ 0.20 $ 0.63 $ 0.60
Dividends declared and paid   $ 0 $ 0 $ 0 $ 0 $ 0 $ 0    
Quarterly dividend | Common Class A                  
Dividends Payable [Line Items]                  
Cash dividends declared per share of Class A common stock $ 0.21                
Non-controlling interest                  
Dividends Payable [Line Items]                  
Dividends declared and paid   0 0 0 0 0 0    
Distributions declared to non-controlling unitholders   $ 2,638 $ 2,638 $ 2,638 $ 2,512 $ 2,512 $ 2,512 $ 7,914 $ 7,536