Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Tax Carryforwards
Increase (decrease) in valuation allowance	$ (178,200,000)	$ 14,800,000	$ 306,400,000
Deferred tax liabilities recognized in other liabilities, excluding current portion	6,341,000	134,063,000
Valuation allowance	1,552,942,000	1,731,186,000
Unrecognized tax benefits	3,800,000	0	$ 400,000
Income tax penalties and interest accrued	0
Variable Interest Entity, Primary Beneficiary
Tax Carryforwards
Deferred tax liabilities recognized in other liabilities, excluding current portion	4,756,000	$ 131,446,000
Internal Revenue Service (IRS)
Tax Carryforwards
Operating loss carryforwards	3,600,000,000
Tax credit carryforwards	312,500,000
State and Local Jurisdiction
Tax Carryforwards
Operating loss carryforwards	880,700,000
Tax credit carryforwards	$ 115,700,000