Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
State tax effected net operating losses
Deferred tax adjustment related to change in overall state tax rate	$ (663)	$ 2,822	$ (86,956)
Alternative minimum tax credits	218,773	228,693
Tax benefits related to employee stock-based compensation not reflected in deferred tax assets	120,300
Additions based on tax provisions related to the current year	0	0	0
Reductions for tax positions of prior years	0	0	3,037
Unrecognized tax benefits	663	$ 663	$ 663	$ 3,700
Federal
State tax effected net operating losses
Net operating loss carryforwards	1,000,000
State Tax Reporting
State tax effected net operating losses
Net operating loss carryforwards	636,100
Valuation allowance on operating loss carryforwards	$ 4,800