Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Federal corporate tax rate (as a percent)		35.00%
Increase (decrease) in valuation allowance		$ 14,600	$ 277,300	$ (126,200)
Deferred tax impact of Tax Cuts and Jobs Act of 2017		196,751
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at beginning of period	$ 18,022	10,798	836
Additions related to prior periods tax positions		2,571	6,740
Reductions related to prior periods tax positions		(821)
Additions related to current period tax positions		5,555	2,652
Acquisitions			570
Reductions due to lapse of applicable statute of limitations		(81)
Balance at end of period		18,022	10,798	$ 836
Accrued interest and penalties		$ 300	$ 300
Forecast
Federal corporate tax rate (as a percent)	21.00%