Organization and Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011		Dec. 31, 2010
Organization and Significant Accounting Policies
Decrease in general mortgage provision allowance	$ 18,240
Consolidated Balance Sheets
Deferred acquisition costs and value of business acquired	204,461	219,833
Deferred income tax liabilities, net	(288,995)	(154,464)
Accumulated other comprehensive income	635,699	469,982
Retained earnings	722,525	668,812
Consolidated Statements of Income
General insurance expenses	596,649	566,693		530,893
Amortization of deferred acquisition costs and value of business acquired	60,479	28,820		29,343
Income tax expense	135,305	93,818		68,627
Net income	238,114	202,237	[1]	195,534	[1]
Consolidated Statements of Comprehensive Income
Net income	238,114	202,237	[1]	195,534	[1]
Future policy benefits, deferred acquisition costs and value of business acquired adjustments	(83,835)	(100,216)		(129,715)
Income tax expense related to items of other comprehensive income	89,232	108,056		220,476
Consolidated Statements of Stockholder's Equity
Accumulated other comprehensive income (loss)	635,699	469,982
Retained earnings	722,525	668,812
Net income	238,114	202,237	[1]	195,534	[1]
Other comprehensive income (loss), net of income taxes	165,717	200,674	[1]	409,454	[1]
Consolidated Statements of Cash Flows
Net income	238,114	202,237	[1]	195,534	[1]
Depreciation and amortization	82,595	48,094		44,540
Deferral of acquisition costs	(94,826)	(57,108)		(47,513)
Deferred income taxes	45,371	23,617		33,636
Adoption of ASU No. 2010-26
Consolidated Balance Sheets
Deferred acquisition costs and value of business acquired		219,833
Deferred income tax liabilities, net		154,464
Accumulated other comprehensive income		469,982		(140,146)
Retained earnings		668,812		638,311
Consolidated Statements of Income
General insurance expenses		566,693		530,893
Amortization of deferred acquisition costs and value of business acquired		28,820		29,343
Income tax expense		93,818		68,627
Net income		202,237		195,534
Consolidated Statements of Comprehensive Income
Net income		202,237		195,534
Future policy benefits, deferred acquisition costs and value of business acquired adjustments		(100,216)		(129,715)
Income tax expense related to items of other comprehensive income		108,056		220,476
Consolidated Statements of Stockholder's Equity
Accumulated other comprehensive income (loss)		469,982		(140,146)
Retained earnings		668,812		638,311
Net income		202,237		195,534
Other comprehensive income (loss), net of income taxes		200,674		409,454
Consolidated Statements of Cash Flows
Net income		202,237		195,534
Depreciation and amortization		48,094		44,540
Deferral of acquisition costs		(57,108)		(47,513)
Deferred income taxes		23,617		30,636
As previously reported | Adoption of ASU No. 2010-26
Consolidated Balance Sheets
Deferred acquisition costs and value of business acquired		343,449
Deferred income tax liabilities, net		197,729
Accumulated other comprehensive income		445,372		(132,721)
Retained earnings		773,773		724,193
Consolidated Statements of Income
General insurance expenses		535,636		498,386
Amortization of deferred acquisition costs and value of business acquired		41,634		50,741
Income tax expense		100,203		72,515
Net income		214,095		202,755
Consolidated Statements of Comprehensive Income
Net income		214,095		202,755
Future policy benefits, deferred acquisition costs and value of business acquired adjustments		(96,860)		(182,357)
Income tax expense related to items of other comprehensive income		109,230		202,051
Consolidated Statements of Stockholder's Equity
Accumulated other comprehensive income (loss)		445,372		(132,721)
Retained earnings		773,773		724,193
Net income		214,095		202,755
Other comprehensive income (loss), net of income taxes		202,856		375,237
Consolidated Statements of Cash Flows
Net income		214,095		202,755
Depreciation and amortization		60,908		65,938
Deferral of acquisition costs		(88,165)		(80,020)
Deferred income taxes		30,002		37,524
Retrospective adoption | Adoption of ASU No. 2010-26
Consolidated Balance Sheets
Deferred acquisition costs and value of business acquired		(123,616)
Deferred income tax liabilities, net		(43,265)
Accumulated other comprehensive income		24,610		(7,425)
Retained earnings		(104,961)		(85,882)
Consolidated Statements of Income
General insurance expenses		31,057		32,507
Amortization of deferred acquisition costs and value of business acquired		(12,814)		(21,398)
Income tax expense		(6,385)		(3,888)
Net income		(11,858)		(7,221)
Consolidated Statements of Comprehensive Income
Net income		(11,858)		(7,221)
Future policy benefits, deferred acquisition costs and value of business acquired adjustments		(3,356)		52,642
Income tax expense related to items of other comprehensive income		(1,174)		18,425
Consolidated Statements of Stockholder's Equity
Accumulated other comprehensive income (loss)		24,610		(7,425)
Retained earnings		(104,961)		(85,882)
Net income		(11,858)		(7,221)
Other comprehensive income (loss), net of income taxes		(2,182)		34,217
Consolidated Statements of Cash Flows
Net income		(11,858)		(7,221)
Depreciation and amortization		(12,814)		(21,398)
Deferral of acquisition costs		31,057		32,507
Deferred income taxes		$ (6,385)		$ (3,888)

[1] As adjusted; See Note 1