Indebtedness (Covenants in the Line of Credit) (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Debt Disclosure [Abstract]
Consolidated net worth, required	$ 824,000,000
Statutory surplus, required	750,000,000
Debt-to-capitalization ratio, required	35.00%
Consolidated net worth, actual	1,090,592,000	1,058,328,000	1,018,041,000
Statutory surplus, actual	$ 1,050,100,000	$ 1,062,700,000
Debt-to-capitalization ratio, actual	20.30%

The amount of statutory capital and surplus (stockholders' equity) as of the balance sheet date using prescribed or permitted statutory accounting practices (rather than GAAP, if different) of the state or country.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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