Supplemental Balance Sheet Information - Other Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Customer contracts and relationships, net	$ 23,484	$ 25,252
Other intangible assets	1,624	1,752
Other	4,671	5,797
Other assets, net	29,779	32,801
Accumulated amortization of intangible assets	$ 41,984	$ 39,462