Fair Value Measurements - Investments in Company-Sponsored Funds (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Investment Holdings [Line Items]
Fair Value	$ 7,473
Unfunded Commitments	1,401
Hedge Funds [Member]
Investment Holdings [Line Items]
Fair Value	2,566
Unfunded Commitments	$ 0
Redemption Frequency	Quarterly - Annually
Investment Redemption Notice Period Minimum	30 days
Investment Redemption Notice Period Maximum	120 days
Private Equity Funds [Member]
Investment Holdings [Line Items]
Investments Lock In Period	10 years
Fair Value	$ 4,907
Unfunded Commitments	$ 1,401
Maximum [Member] | Hedge Funds [Member]
Investment Holdings [Line Items]
Investments Lock In Period	1 year