Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Examination [Line Items]
Federal statutory income tax rate	35.00%	35.00%
Change in deferred tax assets	$ 100,900
Decrease in deferred tax asset valuation allowance	100,900
Valuation allowance	162,708	$ 292,214
Deferred tax assets, related to state operating losses	33,600
Increase in valuation allowance	$ 33,600
Missouri percentage of total federal operating loss	13.00%
Unrecognized tax benefits	$ 328	331	$ 368
Unrecognized tax benefits reductions resulting from lapse of applicable statute of limitations due In next twelve months	100
Accrued interest and penalties	100	$ 100
Internal Revenue Service (IRS)
Income Tax Examination [Line Items]
Federal net operating loss carryforwards	$ 692,000
Minimum
Income Tax Examination [Line Items]
Open tax year	2013
Minimum | Internal Revenue Service (IRS)
Income Tax Examination [Line Items]
Year of operating loss carryforwards expiration	Dec. 31, 2025
Minimum | State and Local Jurisdiction
Income Tax Examination [Line Items]
Year of operating loss carryforwards expiration	Dec. 31, 2017
Maximum
Income Tax Examination [Line Items]
Open tax year	2017
Maximum | Internal Revenue Service (IRS)
Income Tax Examination [Line Items]
Year of operating loss carryforwards expiration	Dec. 31, 2037
Maximum | State and Local Jurisdiction
Income Tax Examination [Line Items]
Year of operating loss carryforwards expiration	Dec. 31, 2037
Mortgage Security | Internal Revenue Service (IRS)
Income Tax Examination [Line Items]
Federal net operating loss carryforwards	$ 307,300