Workforce Reduction - Roll Forward (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Workforce Reduction
Balance at beginning of period	$ 0
Charges	2,422
Amounts Paid	(1,067)
Non-cash Expense	(194)
Balance at end of period	1,161
Employee severance, benefits and related costs
Workforce Reduction
Balance at beginning of period	0
Charges	2,422
Amounts Paid	(1,067)
Non-cash Expense	(194)
Balance at end of period	$ 1,161