XML 62 R47.htm IDEA: XBRL DOCUMENT

Employee Benefit Plan (Details) - USD ($)	12 Months Ended
Employee Benefit Plan (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Defined contribution plan, maximum annual contribution by employee, percent of eligible earnings (up to)	80.00%
Defined contribution plan, employer matching contribution per employee, amount (up to)	$ 1,500
Defined contribution plan, period after which cliff vest occurs (in years)	1 year
Defined contribution plan, employer discretionary contribution amount	$ 2,000,000	$ 1,900,000	$ 2,100,000