Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
State tax effected net operating losses
TCJA tax benefit	$ 11,400	$ 242,900
Effective tax rate	20.21%	143.95%	36.76%
Alternative minimum tax credits	$ 114,149	$ 208,624
Valuation allowance	14,943	16,711
Unrecognized tax benefits	16,850	$ 663	$ 663	$ 663
Liability for accrued interest	3,100
Federal
State tax effected net operating losses
Net operating loss carryforwards	142,600
State Tax Reporting
State tax effected net operating losses
Net operating loss carryforwards	468,100
Valuation allowance on operating loss carryforwards	$ 14,100
Excluding Impact of Tax Reform
State tax effected net operating losses
Effective tax rate	21.80%	37.60%
Refundable Portion Of AMT Credits
State tax effected net operating losses
TCJA tax benefit	$ 10,700
Valuation allowance		$ 10,700