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Shareholders' Equity (Narrative) (Details)
$ / shares in Units, $ in Thousands
 2 Months Ended 12 Months Ended
May 31, 2014
USD ($)
Dec. 31, 2016
USD ($)
vote
$ / shares
shares
Dec. 31, 2015
USD ($)
$ / shares
shares
Dec. 31, 2014
USD ($)
shares
Dec. 31, 2013
$ / shares
shares
Class of Stock [Line Items]          
Common stock, shares authorized   500,000,000      
Common stock, par value (in dollars per share) | $ / shares   $ 0      
Common stock, shares issued   210,711,224 210,538,896 210,216,043 209,867,426
Common stock, shares outstanding   210,711,224 210,538,896 210,216,043 209,867,426
Common stock dividends declared | $   $ 0 $ 0 $ 50,036  
Dividends payable | $     $ 12,509    
Salary period paid upon employee leaving   30 days      
Class A Shares Of Common Stock [Member]          
Class of Stock [Line Items]          
Common stock, shares authorized   420,000,000 420,000,000    
Common stock, par value (in dollars per share) | $ / shares   $ 0 $ 0   $ 0
Common stock, shares issued   130,711,224 130,538,896 130,216,043 129,867,426
Common stock, shares outstanding   130,711,224 130,538,896 130,216,043 129,867,426
Shares issued during the period   172,328 322,853 348,617  
Number of votes per share (in votes) | vote   1      
Class B Shares Of Common Stock [Member]          
Class of Stock [Line Items]          
Common stock, shares authorized   80,000,000 80,000,000    
Common stock, par value (in dollars per share) | $ / shares   $ 0 $ 0    
Common stock, shares issued   80,000,000 80,000,000 80,000,000 80,000,000
Common stock, shares outstanding   80,000,000 80,000,000 80,000,000 80,000,000
Number of votes per share (in votes) | vote   5      
2011 Equity Incentive Plan [Member] | Restricted Share Units [Member]          
Class of Stock [Line Items]          
Dividends | $ $ 382