Accounts Receivable and Allowance for Doubtful Accounts - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable Allowance For Credit Losses [Line Items]
Long-term receivables more than 90 days past due	$ 2.7	$ 2.2
Placement Fee Receivable
Financing Receivable Allowance For Credit Losses [Line Items]
Long-term receivables	$ 73.1	$ 62.6
Minimum
Financing Receivable Allowance For Credit Losses [Line Items]
Accounts receivable payment terms	3 years
Maximum
Financing Receivable Allowance For Credit Losses [Line Items]
Accounts receivable payment terms	4 years