Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018
Schedule Of Income Taxes [Line Items]
Income tax expense due to re-measurement of deferred tax assets and liabilities as result of changes in federal tax rate	$ 13,400
Income tax benefit		$ 3,000
Valuation allowance related to gross deferred tax assets	$ 3,598	4,573
Deferred tax assets, net operating loss carry forwards		$ 45,800
Minimum
Schedule Of Income Taxes [Line Items]
Deferred tax assets, net operating loss carry forwards, expiration date		2020
Maximum
Schedule Of Income Taxes [Line Items]
Deferred tax assets, net operating loss carry forwards, expiration date		2039
PENNSYLVANIA
Schedule Of Income Taxes [Line Items]
Valuation allowance related to gross deferred tax assets		$ 4,600