Schedule IV Reinsurance (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums, Life Insurance in Force									$ 781,495.9	$ 832,587.5	$ 782,935.6
Ceded Premiums, Life Insurance in Force									25,904.7	28,658.7	28,341.1
Assumed Premiums, Life Insurance in Force									1,026.2	1,073.8	1,141.6
Premiums, Net, Life Insurance in Force									756,617.4	805,002.6	755,736.1
Life Insurance in Force Premiums, Percentage Assumed to Net									0.10%	0.10%	0.20%
Gross Amount									7,777.3	7,736.0	7,521.5
Reinsurance Ceded									355.8	230.8	223.9
Assumed Premiums Earned									203.2	210.9	216.6
Net Amount	1,890.7	1,897.3	1,905.8	1,930.9	1,937.2	1,929.4	1,927.6	1,921.9	7,624.7	7,716.1	7,514.2
Percentage of Amount Assumed to Net									2.70%	2.70%	2.90%
Life Insurance Product Line
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount									2,018.7	1,979.1	1,868.8
Reinsurance Ceded									253.6	141.4	146.6
Assumed Premiums Earned									10.0	10.3	10.9
Net Amount									1,775.1	1,848.0	1,733.1
Percentage of Amount Assumed to Net									0.60%	0.60%	0.60%
Accident and Health Insurance Segment
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount									5,758.6	5,756.9	5,652.7
Reinsurance Ceded									102.2	89.4	77.3
Assumed Premiums Earned									193.2	200.6	205.7
Net Amount									$ 5,849.6	$ 5,868.1	$ 5,781.1
Percentage of Amount Assumed to Net									3.30%	3.40%	3.60%