Commitments And Contingencies (Details) $ / shares in Units, $ in Thousands	1 Months Ended		9 Months Ended			12 Months Ended			114 Months Ended
	Mar. 31, 2018 $ / shares shares	Sep. 30, 2017 USD ($) item	Sep. 30, 2018 USD ($) store item	Sep. 30, 2017 USD ($)		Dec. 31, 2017 USD ($)		Dec. 31, 2015	Jun. 30, 2017 USD ($)
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Payments to subsidies			$ 2,200	$ 1,700
Accrued liabilities and other			$ 94,729			$ 77,317	[1]
Number of HOAs, subsidies provided to | item			10
Inventory purchased			$ 23,405	30,707	[1]
Number of opt-ins | item		80	59
Average annual default rates			8.40%					6.90%
Percent of total delinquencies subject to letters			16.80%
Accrued liabilities			$ 3,700
Purchase period, from lawsuit			6 years
Period which plaintiffs received calls			12 months
Stock Appreciation Rights (SARs) [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Awards vesting period			5 years
Performance Units [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Period of awards right to receive cash payment			2 years
Implemented Initiative, Streamline Operations In Certain Areas, Facilitate Future Growth [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Severance expense						5,800
Amount of future payment			$ 400
Subsidies To Certain HOAs [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Accrued liabilities and other			$ 6,200			$ 0
Executive Officers [Member] | Stock Appreciation Rights (SARs) [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Percent of awards granted			30.00%
Executive Officers [Member] | Performance Units [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Percent of awards granted			70.00%
Senior Vice Presidents [Member] | Performance Units [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Percent of awards granted			100.00%
Executive [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Amount of future payment		$ 2,900	$ 1,200	$ 2,900
Officers [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Amount of future payment			$ 7,400
Approved for grants | shares	639,643
Approved for grants, exercise price | $ / shares	$ 19.72
Bass Pro [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Number of stores vacation packages are sold | store			69
Compensation paid under agreement on sales			$ 0
Percent of volume sales from agreement			14.00%	15.00%
Aggregate amount of purchaser default adjustments									$ 4,800

[1] * See Note 2 for summary of adjustments.