Income Taxes (Components of Net Deferred Income Taxes) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 197,017	$ 212,253
Lease liability	14,517	16,772
Deferred revenues	14,483	5,095
Deferred compensation	6,138	8,146
Accrued salaries and benefits	3,499	2,406
Tax credits	2,187	2,945
Tax contingencies	1,132	1,127
Allowance for doubtful accounts	776	453
Capital loss carryforwards	263	266
Goodwill	0	2,462
Litigation settlement	0	225
Other	2,550	2,409
Gross deferred tax assets	242,562	254,559
Valuation allowance	(220,115)	(219,607)	$ (200,366)
Net deferred tax assets	22,447	34,952
Deferred tax liabilities:
Lease asset	(8,829)	(11,219)
Property and equipment	(5,716)	(5,134)
Intangible assets	(3,495)	(15,202)
Subpart F income recapture	(1,224)	(1,224)
Goodwill	(958)	0
Other	(111)	(86)
Total deferred tax liabilities	(20,333)	(32,865)
Net deferred tax asset	$ 2,114	$ 2,087