Indemnity Accumulated Other Comprehensive Income (Loss) (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Amounts reclassified out of accumulated other comprehensive income (loss) and the related affected line item in the Consolidated Statements of Operations where net income is presented
Net realized investment gains	$ 249	$ 296
Net impairment losses recognized in earnings	0	0
Income (loss) from operations before income taxes and noncontrolling interest	436	534
Provision for income taxes	146	180
Net income (loss)	290	354	619
Less: Net income attributable to noncontrolling interest in consolidated entity – Exchange	253	318
Net income attributable to Indemnity	37	36
Amounts reclassified from accumulated other comprehensive income (loss)(1)
Amounts reclassified out of accumulated other comprehensive income (loss) and the related affected line item in the Consolidated Statements of Operations where net income is presented
Net income attributable to Indemnity	0
Unrealized holding gains (losses) on available-for-sale securities | Amounts reclassified from accumulated other comprehensive income (loss)(1)
Amounts reclassified out of accumulated other comprehensive income (loss) and the related affected line item in the Consolidated Statements of Operations where net income is presented
Net realized investment gains	15
Net impairment losses recognized in earnings	0
Income (loss) from operations before income taxes and noncontrolling interest	15
Provision for income taxes	5
Net income (loss)	10
Less: Net income attributable to noncontrolling interest in consolidated entity – Exchange	10
Net income attributable to Indemnity	0
Amortization of postretirement plan items | Amounts reclassified from accumulated other comprehensive income (loss)(1)
Amounts reclassified out of accumulated other comprehensive income (loss) and the related affected line item in the Consolidated Statements of Operations where net income is presented
Net income attributable to Indemnity	$ 0