Investments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Investments [Line Items]
Fair value of fixed maturity securities	$ 42,344,400,000	$ 44,973,000,000
Fair value of fixed maturity securities, gross unrealized gain	4,358,700,000	7,277,500,000
Fair Value of fixed maturity securities, gross unrealized loss	303,900,000	56,000,000
Fixed Maturity Securities Other Than Temporary Impairments in Accumulated Other Comprehensive Income Loss	0	0	1
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held			8,500,000
Commitment to fund private placement fixed maturity securities	58,000,000
Carrying amount of variable interest entity investments	470,800,000
Unfunded commitment to fund Investment Partnerships	27,200,000
Commitment to fund partnership Equity Investments	158,400,000
Other Long-term Investments	566,000,000	625,000,000
Commitments to Fund Special Purpose Entities	0
Amount Funded to Special Purpose Entity Partnerships	nor did we fund any amounts to the partnerships	nor did we fund any amounts to the partnership	nor did we fund any amounts to the partnership
Mortgage Loan policy is not to exceed a loan-to-value ratio, percent	75.00%
Loan to Value Ratio Update Frequency	3 years
Mortgage Loan Inspection Frequency	2 years
Mortage Loan Policy Debt Service coverage ratio lower range	125.00%
Mortgage Loans issuance, term years	25
Number of Changes to Accounting Policy for Estimating Credit Losses on Mortgage Loans	0
Impaired Financing Receivable, Average Recorded Investment	14,900,000	19,100,000	21,300,000
Impaired Financing Receivable, Interest Income, Accrual Method	800,000	800,000	800,000
Foreclosed Real Estate Expense	0	0	0
Financing Receivable, Recorder Investment, Nonaccrual status	0	1
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	4,300,000
Committments to Fund Commercial Mortgage Loans	83,900,000
Repurchase agreements - Typical Days outstanding	30
Minimum percent of the fair value of securities loaned or securities purchased under repurchase agreements be maintained as collateral	102.00%
Securities Loaned	201,600,000	452,800,000
Outstanding Repurchase Agreements	0	0
Off Balance Sheet Amount
Schedule of Investments [Line Items]
Cash Collateral for Borrowed Securities	76,500,000	455,800,000
Securities Received as Collateral	132,900,000	14,500,000
Nonperforming Financing Receivable [Member]
Schedule of Investments [Line Items]
Amount of days past due-DelinquentMortgageLoan	90 days	90 days
Special Purpose Entity | Bonds
Schedule of Investments [Line Items]
Fair value of fixed maturity securities	136,200,000
Special Purpose Entity | Partnership Interest
Schedule of Investments [Line Items]
Other Long-term Investments	4,400,000
Partnership Interests In Tax Credit Investments
Schedule of Investments [Line Items]
Carrying amount of variable interest entity investments	309,500,000
Equity Method Investments
Schedule of Investments [Line Items]
Carrying amount of variable interest entity investments	161,300,000
External Credit Rating, Investment Grade
Schedule of Investments [Line Items]
Fair value of fixed maturity securities	39,145,100,000
Fair value of fixed maturity securities, gross unrealized gain	4,205,000,000
Fair Value of fixed maturity securities, gross unrealized loss	247,800,000
Fixed maturity securities in unrealized loss position, percent of total	81.50%
Number of fixed maturity securities that were in an unrealized loss position	245
Number of fixed maturity securities in an unrealized loss position continuously for over one year	16
External Credit Rating, Non Investment Grade
Schedule of Investments [Line Items]
Fair value of fixed maturity securities	3,199,300,000
Fair value of fixed maturity securities, gross unrealized gain	153,700,000
Fair Value of fixed maturity securities, gross unrealized loss	$ 56,100,000
Fixed maturity securities in unrealized loss position, percent of total	18.50%
Number of fixed maturity securities that were in an unrealized loss position	53
Number of fixed maturity securities in an unrealized loss position continuously for over one year	8