Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
State tax effected net operating losses
Alternative minimum tax credits	$ 228,693	$ 227,719
Tax benefits related to employee stock-based compensation not reflected in deferred tax assets	117,800
Deferred tax adjustment related to change in overall state tax rate	2,822	(86,956)	$ 15,220
Additions based on tax provisions related to the current year	0	0	3,700
Reductions for tax positions of prior years	0	3,037	0
Unrecognized tax benefits	663	$ 663	$ 3,700	$ 0
Federal
State tax effected net operating losses
Net operating loss carryforwards	685,300
State Tax Reporting
State tax effected net operating losses
Net operating loss carryforwards	530,400
Valuation allowance on operating loss carryforwards	$ 4,600