Fair Value Measurements (Details) - Fair Value Measurements on a Recurring Basis $ in Thousands	Mar. 31, 2018 USD ($)
Fair Value Measurements (Textual)
Cost basis of investment funds	$ 57,537
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Deferred compensation plan assets	34,806
Liabilities:
Deferred compensation plan liabilities	70,200
Significant Other Observable Inputs (Level 2)
Assets:
Deferred compensation plan assets	26,450
Fair Value
Assets:
Deferred compensation plan assets	61,256
Liabilities:
Deferred compensation plan liabilities	$ 70,200