Significant Accounting Policies (Policy)	3 Months Ended
Significant Accounting Policies (Policy)	Mar. 31, 2012
Significant Accounting Policies [Abstract]
Basis Of Presentation	*Basis of Presentation* The accompanying unaudited consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X and, accordingly, do not include all of the information and disclosures required by GAAP for annual periods. These statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Annual Report on Form 10-K for the year ended December 31, 2011. The accompanying consolidated financial statements have not been audited by an independent registered public accounting firm in accordance with the standards of the Public Company Accounting Oversight Board (U.S.), but in the opinion of management such financial statements include all adjustments, consisting only of normal recurring adjustments, necessary for the fair statement of the Company's consolidated financial position and results of operations. All material intercompany balances and transactions have been eliminated. The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. As additional information becomes available or actual amounts become determinable, the recorded estimates are revised and reflected in operating results. The results of operations for the three months ended March 31, 2012 may not be indicative of the results that may be expected for the year ending December 31, 2012. The December 31, 2011 consolidated balance sheet was derived from audited financial statements, but does not include all disclosures required by GAAP for annual periods. Certain amounts have been reclassified in prior years' financial statements to conform to the current presentation. Such reclassifications had no impact on total revenues, expenses, assets, liabilities, or shareholders' equity for all periods presented. During the second quarter of 2011, the Company identified a model input error related to the measurement of fair value and associated unrealized losses on certain insured derivatives. This error related to the quarter ended March 31, 2011 and had understated pre-tax mark-to-market loss by $207 million. The Company assessed the materiality of the error in accordance with Securities and Exchange Commission ("SEC") Staff Accounting Bulletin No. 99, Materiality, and concluded that this error was not material to the consolidated financial statements as of and for the three months ended March 31, 2011 and did not affect any prior consolidated financial statements. However, the cumulative effect of the error was determined to be material if the correction was recorded in the consolidated financial statements as of and for the three months ended June 30, 2011. In accordance with SEC Staff Accounting Bulletin No. 108, Considering the Effects of Prior Year Misstatements When Quantifying Misstatements in Current Year Financial Statements, the consolidated financial statements as of and for the three months ended March 31, 2011 were revised in the Company's Quarterly Report on Form 10-Q for the period ended June 30, 2011 and are reflected in the prior years' financial statements included in the Quarterly Report on Form 10-Q for the period ended March 31, 2012.
Statements Of Cash Flows	*Statements of Cash Flows* Previously, the Company reported its consolidated statements of cash flows using the indirect method. The indirect method uses accrual accounting information to present the cash flows from operations. As of March 31, 2012, the Company elected to present its Statements of Cash Flows using the direct method. The direct method uses actual cash flow information from the Company's operations, rather than using accrual accounting values. Using either the direct or indirect method, total cash flows from operations are the same. In addition, the presentation of cash flows from investing and financing activities using either the direct or indirect method are the same. The change to the direct method for calculating and presenting cash flows from operations was implemented retroactively for all statements of cash flows presented herein. Use of the direct method requires a reconciliation of net income to cash flows from operations. This reconciliation is provided as a supplement directly beneath the statements of cash flows.