Restructuring Activities and Other Charges (Details) $ in Thousands		3 Months Ended
	Dec. 14, 2015 USD ($) employee	Mar. 31, 2018 USD ($)
Restructuring Reserve [Roll Forward]
Balance at December 31, 2017		$ 484
Cash payments		(47)
Balance at March 31, 2018		437
Number of positions eliminated | employee	100
Restructuring charges	$ 6,700	0
Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Balance at December 31, 2017		484
Cash payments		(47)
Balance at March 31, 2018		437
Restructuring charges	5,600
Contract Termination [Member]
Restructuring Reserve [Roll Forward]
Balance at December 31, 2017		0
Cash payments		0
Balance at March 31, 2018		0
Restructuring charges	$ 1,100
Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Balance at December 31, 2017		0
Cash payments		0
Balance at March 31, 2018		$ 0