Restructuring and Special Charges - Rollforward (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Balance at December 31,	$ 2,265,000	$ 9,413,000	$ 7,157,000
Additions	0	0	12,084,000
Adjustments to accruals	(1,301,000)	(2,187,000)	(520,000)
Cash payments	(150,000)	(4,961,000)	(9,308,000)
Balance at December 31,	814,000	2,265,000	9,413,000
Deferred rent
Restructuring Reserve [Roll Forward]
Balance at December 31,	1,302,000	2,846,000	3,066,000
Additions	0	0	1,277,000
Adjustments to accruals	(1,302,000)	(1,544,000)	(1,497,000)
Cash payments	0	0	0
Balance at December 31,	0	1,302,000	2,846,000
Accrued compensation and related costs
Restructuring Reserve [Roll Forward]
Balance at December 31,	477,000	4,782,000	1,525,000
Additions	0	0	10,299,000
Adjustments to accruals	0	0	0
Cash payments	(135,000)	(4,305,000)	(7,042,000)
Balance at December 31,	342,000	477,000	4,782,000
Accounts payable
Restructuring Reserve [Roll Forward]
Balance at December 31,	0	0	617,000
Additions	0	0	195,000
Adjustments to accruals	0	0	0
Cash payments	0	0	(812,000)
Balance at December 31,	0	0	0
Other accrued liabilities
Restructuring Reserve [Roll Forward]
Balance at December 31,	486,000	1,785,000	1,949,000
Additions	0	0	313,000
Adjustments to accruals	1,000	(643,000)	977,000
Cash payments	(15,000)	(656,000)	(1,454,000)
Balance at December 31,	$ 472,000	$ 486,000	$ 1,785,000