Income Taxes - Unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Unrecognized tax benefits
Balance at beginning of year	$ 11,000	$ 11,000	$ 11,000
Reductions for tax positions of prior years	(11,000)	0	0
Balance at end of year	0	$ 11,000	$ 11,000
U.S Federal
Income Taxes
Net operating loss carryforward	1,500,000
State
Income Taxes
Net operating loss carryforward	$ 1,400,000