Investments - Narrative (Details) - Short-term investments	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, weighted average maturity	2 months 15 days	4 months 6 days
Minimum
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, maturity ranges	1 month	1 month
Maximum
Schedule of Available-for-sale Securities [Line Items]
Short-term investments, maturity ranges	12 months	12 months