Summary of Significant Accounting Policies - 401(k) Defined Contribution Plan (Details) - 401(k) Defined Contribution Plan - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution (percent)	100.00%
Maximum annual contributions per employee (percent)	6.00%
Maximum annual contributions per employee	$ 3,000
Compensation expense	$ 1,200,000	$ 1,000,000	$ 600,000