Description of Business and Significant Accounting Policies (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) financial_institution	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segment financial_institution	Jun. 30, 2018 USD ($)	Dec. 31, 2018 financial_institution
Schedule of Accounting Policies [Line Items]
Renewal term			1 year
Number of reportable segments | segment			2
Amortization period of inventories and supplies			24 months
Goodwill and intangible asset impairment			$ 0	$ 0
Revenue	$ 462,101,000	$ 501,587,000	938,212,000	1,002,149,000
Costs of services provided	400,485,000	436,287,000	827,750,000	905,283,000
Investment and other income, net	$ 1,393,000	2,845,000	$ 6,596,000	4,385,000
Number of financial institutions holding cash and cash equivalents and marketable securities | financial_institution	1		1		1
Prior period adjustment
Schedule of Accounting Policies [Line Items]
Revenue		(2,100,000)		(3,400,000)
Costs of services provided		(1,300,000)		(2,200,000)
Investment and other income, net		$ (800,000)		$ (1,200,000)