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Employee Benefit Plans Employee Benefit Plans (Details) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2007
Compensation and Retirement Disclosure [Abstract]        
Eligibility period for 401K savings plan, number of months 3 months      
Defined Contribution Plan - maximum participant deferral percent 60.00%      
Defined Contribution Plan - employer match per dollar of participant contribution $ 0.50      
Defined Contribution Plan - maximum employer match percentage 10.00%      
Defined Contribution Plan - contributions made $ 1,200,000 $ 1,100,000 $ 1,000,000  
Deferred Compensation - maximum participant deferral percent       70.00%
Deferred Compensation - maximum director fees and bonuses that may be deferred (percent)       100.00%
Deferred Compensation - mandatory Company contributions as percentage of gross monthly salary (percent)       10.00%
Deferred Compensation - liability under Plan $ 14,700,000 $ 12,800,000