Supplemental Balance Sheet, Income Statement and Cash Flow Information - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accrued liabilities
Accrued compensation	$ 112,277	$ 116,775
Deferred revenue	241,812	255,626
Other taxes payable	25,306	16,419
Workers' compensation liabilities	18,255	18,255
Interest payable	21,187	57,233
Litigation reserves	19,675	24,896
Current liability to discontinued operations	6,063	5,462
Dividends declared and payable	17,153	17,039
Other accrued liabilities	23,619	31,543
Accrued liabilities	$ 485,347	$ 543,248