Leadership Changes and Restructuring Activities - Rollforward of Estimated Fair Value Liability Established for Total Severance and Other Related Costs (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Balance, January 1	$ 1,973,000	$ 2,408,000
Severance and other related expenses	1,055,000	1,091,000
Accretion	59,000	82,000
Cash payments	(1,792,000)	(1,392,000)
Non-cash adjustment	(2,330,000)	(1,453,000)	$ (2,002,000)
Balance, December 31	964,000	1,973,000	2,408,000
Restricted Stock Units (RSUs)
Restructuring Cost and Reserve [Line Items]
Non-cash adjustment	(2,330,000)	(1,453,000)	(2,002,000)
Separation and Transition Agreement or Retirement Agreement
Restructuring Cost and Reserve [Line Items]
Non-cash adjustment	$ (331,000)	$ (216,000)
Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Severance and other related expenses			$ 1,303,000