Fair Value Measurements - Summary of Fair Value Assets and Liability Measured on Recurring Basis (Parenthetical) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Aug. 11, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized gains on the investments after-tax	$ 421,000		$ 346,000
Earnout contingent consideration liability | ON Services
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Earnout contingent consideration	0	$ 540,000
Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Realized gains on the investments	0
Unrealized gains on the investments	0
Other mutual funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized gains on the investments	700,000		600,000
Unrealized gains on the investments after-tax	$ 400,000		$ 300,000