Investments - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended	12 Months Ended
	Dec. 31, 2011 Investment	Dec. 31, 2010	Dec. 31, 2009	Dec. 02, 2011 Pending or Threatened Litigation	Dec. 31, 2011 Pending or Threatened Litigation	Dec. 31, 2011 State Insurance departments	Dec. 31, 2010 State Insurance departments	Dec. 31, 2011 UK Bank	Dec. 31, 2011 Mortgage-backed and asset-backed securities Year	Dec. 31, 2011 Non Government backed Securities	Dec. 31, 2010 Non Government backed Securities	Dec. 31, 2011 Non Government backed Securities Maximum	Dec. 31, 2010 Non Government backed Securities Maximum	Dec. 31, 2011 Equity Securities Maximum
Schedule of Investments [Line Items]
Securities, effective maturities									3.6
Gross Unrealized Loss										$ 1,400,000	$ 700,000
Percentage of fair value over cost														80.00%
Investment expenses	7,595,000	2,327,000	2,542,000	4,700,000	4,700,000
Number of significant fair value hierarchy classification judgments	0
Fixed maturities, securities deposited						10,200,000	10,900,000
Fixed maturities, securities deposited								1,200,000
Investments pledged under a reinsurance treaty	$ 300,000	$ 300,000
Percentage of investment												5.00%	5.00%