Credit Agreement (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Mar. 31, 2017
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 153,000	$ 150,000
Maximum Borrowing Capacity	$ 200,000
Expiration Date	Feb. 24, 2021
Letters of Credit Outstanding	$ 3,150
Remaining Borrowing Capacity	$ 150,000