Segments of Business - Additional Information (Detail) (USD $)	3 Months Ended			0 Months Ended
	Mar. 31, 2014 Segment	Mar. 31, 2013 Segment	Dec. 31, 2013	Jan. 02, 2014 Kentucky Trailer	Aug. 30, 2013 Kentucky Trailer	Mar. 31, 2014 Reinsurance Segment	Mar. 31, 2014 Insurance Segment	Mar. 31, 2014 Corporate activities
Segment Reporting Information [Line Items]
Acquisition price				$ 15,000,000	$ 24,900,000
Ownership interest percentage					35.40%
Ownership interest acquired				80.00%
Number of reportable segments	2	2
Identifiable assets	23,494,336,000		23,361,088,000			16,500,000,000	6,300,000,000	700,000,000
Cash and invested assets						14,300,000,000	4,800,000,000	400,000,000
Stockholders' equity	$ 7,128,056,000		$ 6,923,757,000			$ 4,500,000,000	$ 2,800,000,000	$ (200,000,000)