Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
State tax effected net operating losses
Effective tax rate	16.84%	24.34%	20.21%
Alternative minimum tax credits	$ 0	$ 22,120
Valuation allowance on deferred tax benefits related to equity method investments	28,231	31,763
Unrecognized tax benefits	6,484	$ 520	$ 16,850	$ 663
Liability for accrued interest	600
State
State tax effected net operating losses
Net operating loss carryforwards	382,500
Valuation allowance on operating loss carryforwards	13,100
Research and development tax credits
State tax effected net operating losses
Unrecognized tax benefits	6,000
Liability for accrued interest	500
Capital loss carryforward
State tax effected net operating losses
Tax credit carryforward	72,200
Tax credit carryforwards valuation allowance	$ 14,900