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Fair Value Measurements - Narrative (Details) - USD ($)
$ in Thousands
Jun. 30, 2018
Mar. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading investments for deferred compensation plan $ 20,005 $ 17,748
Equity method investments 5,300 5,100
Cost method investments 7,300  
Cost method investments   7,300
Fair Value, Measurements, Recurring | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Trading investments for deferred compensation plan $ 20,005 $ 17,748