Fair Value Measurements - Fair Value of Financial Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial liabilities	$ 5,089	$ 4,414
Fair Value Measurements Using Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial liabilities	5,089	4,414
Contingent Acquisition Consideration Payable
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial liabilities	4,380	4,278
Contingent Acquisition Consideration Payable | Fair Value Measurements Using Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial liabilities	4,380	4,278
Asset Retirement Obligation
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial liabilities	709	136
Asset Retirement Obligation | Fair Value Measurements Using Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial liabilities	$ 709	$ 136