Organization and Basis of Presentation (Details) (USD $)	12 Months Ended
	Dec. 31, 2011
Deferred Policy Acquisition Costs [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	$ 4,013,984,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	(470,059,000)
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	3,543,925,000
Future policy benefits [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	9,903,503,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	383,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	9,903,886,000
Deferred Income Taxes [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	1,831,869,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	(152,035,000)
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	1,679,834,000
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	3,131,934,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	(313,505,000)
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	2,818,429,000
Accumulated Other Comprehensive Income (Loss) [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	1,623,055,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	(4,902,000)
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	1,618,153,000
Policy Acquisition Costs And Other Insurance Expenses [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	331,153,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	15,094,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	346,247,000
Income Before Income Taxes [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	241,849,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	(15,094,000)
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	226,755,000
Provision For Income Taxes [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	81,033,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	(3,198,000)
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	77,835,000
Net Income [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	160,816,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	(11,896,000)
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	148,920,000
Basic Earnings Per Share [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	2.20
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	(0.17)
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	2.03
Diluted Earnings Per Share [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	2.18
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	(0.16)
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	2.02
Change In Operating Assets And Liabilities Deferred Policy Acquisition Costs [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	67,230,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	15,094,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	82,324,000
Change In Operating Assets And Liabilities Deferred Income Taxes [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount before Application	23,517,000
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount of Application Adjustment	(3,198,000)
Retrospective Effect of Change in Accounting Principle, Tabular Presentation by Financial Statement Line Item, Amount after Application	$ 20,319,000