Background and Business Description Rehabilitation Exit Support Agreement (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Apr. 29, 1991	Dec. 31, 2015	Dec. 31, 2021	Dec. 31, 2020	May 01, 2013	Apr. 30, 2013
Preferred Stock, Shares Outstanding			0	0
Entity Incorporation, Date of Incorporation	Apr. 29, 1991
Common stock, shares authorized			130,000,000	130,000,000
Common Stock, Par or Stated Value Per Share						$ 0.01
Preferred stock, shares authorized			20,000,000	20,000,000
Preferred Stock, Par or Stated Value Per Share			$ 0.01			$ 0.01
Common stock, shares issued			46,477,068	45,865,081
Class of Warrant or Right, Exercise Price of Warrants or Rights					$ 16.67
Common Stock Voting Restrictions	10.00%
Common Stock Voting Restriction Less One Vote	10.00%
Common Stock Transfer Restrictions	5.00%
Common Stock Additional Transfer Restrictions		5.00%
Stockholders' Equity Attributable to Noncontrolling Interest			$ 60	$ 60
Market Value of Secured Note Collateral			$ 0	$ 178
Ambac Assurance Corporation [Member]
Preferred Stock, Shares Outstanding			5,501	5,501
Preferred Stock, Liquidation Preference, Value			$ 138	$ 138
Long-term Debt [Member]
Gain Contingency, Unrecorded Amount			$ 1,400