Revenue - Balance Sheet, Impact of Adoption (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets
Accounts receivable, net	$ 241,841	$ 244,518	$ 244,416
Other current assets	44,623	40,171	41,799
Deferred tax assets		43,617
Other assets	37,393	23,566	15,504
Liabilities
Deferred revenue	60,547	55,738	55,738
Noncurrent contingent and other liabilities	7,179	29,292	28,801
Stockholders’ equity
Retained earnings	406,247	$ 407,218	$ 402,544
Amounts in Accordance with ASC 606
Assets
Accounts receivable, net	241,841
Other current assets	44,623
Deferred tax assets	39,449
Other assets	37,393
Liabilities
Deferred revenue	60,547
Noncurrent contingent and other liabilities	7,179
Stockholders’ equity
Retained earnings	406,247
Amounts in Accordance with ASC 605
Assets
Accounts receivable, net	236,438
Other current assets	46,981
Deferred tax assets	41,702
Other assets	28,840
Liabilities
Deferred revenue	60,837
Noncurrent contingent and other liabilities	6,924
Stockholders’ equity
Retained earnings	396,867
Effect of change higher (lower) | Effect of change higher (lower)
Assets
Accounts receivable, net	5,403
Other current assets	(2,358)
Deferred tax assets	(2,253)
Other assets	8,553
Liabilities
Deferred revenue	(290)
Noncurrent contingent and other liabilities	255
Stockholders’ equity
Retained earnings	$ 9,380