Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
General Electric Company
Schedule Of Significant Accounting Policies [Line Items]
Percentage of accounts receivables	15.00%	18.00%
Percentage of revenues	16.00%	19.00%	20.00%
Minimum
Schedule Of Significant Accounting Policies [Line Items]
Short term investment, maturity period	90 days
Maximum
Schedule Of Significant Accounting Policies [Line Items]
Short term investment, maturity period	1 year