Schedule II - Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 0	$ 0	$ 80
Charged to costs and expenses	0	0	0
Charged to other accounts	0	0	0
Deductions	0	0	(80)
Balance at end of period	0	0	0
Valuation allowance on deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	69,753	37,173	69,508
Charged to costs and expenses	8,265	32,580	0
Charged to other accounts	0	0	0
Deductions	0	0	(32,335)
Balance at end of period	$ 78,018	$ 69,753	$ 37,173