Investments - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012 Security	Dec. 31, 2011
Investments [Line Items]
Percentage of future claim payments made in cash	25.00%
Percentage of future claim payments made in surplus note	75.00%
12 Months or Longer, Gross Unrealized Loss	$ 80,767,000	$ 114,011,000
Unrealized losses of one security under closed-block life insurance issuance	2,879,000
Unrealized losses of one security of large diversified financial services company	3,846
Period of unrealized loss position on large diversified financial services company	63 months
Unrealized loss position of Alt-A securities greater than twelve months	23,867,000
Percentage of unrealized losses on mortgage-backed securities attributable to Alt-A Securities	99.90%
Number of individual Alt-A securities	17
Unrealized losses on security secured by IRS facility lease payments	30,747,000
Percentage of permitted policy claim	25.00%
Securities fair value	7,065,000	7,132,000
Securities fair value	194,172,000	172,880,000
Minimum [Member]
Investments [Line Items]
Period of unrealized loss position on closed-block life insurance Issuance	39 months
Period of unrealized loss position on security secured by IRS facility lease payments	16 months
Maximum [Member]
Investments [Line Items]
Period of unrealized loss position on closed-block life insurance Issuance	57 months
Period of unrealized loss position on security secured by IRS facility lease payments	57 months
Below Investment Grade Securities And Non Rated Securities [Member]
Investments [Line Items]
Fair value of below investment grade securities and non-rated securities	242,028,000	268,633,000
Gross Unrealized loss	56,568,000	77,947,000
Other Asset-backed Securities [Member]
Investments [Line Items]
12 Months or Longer, Gross Unrealized Loss	47,745,000
Residential Mortgage-backed securities [Member]
Investments [Line Items]
12 Months or Longer, Gross Unrealized Loss	23,878,000	43,321,000
Corporate Obligations [Member]
Investments [Line Items]
12 Months or Longer, Gross Unrealized Loss	$ 8,541,000	$ 16,983,000