Investments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended						3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended			3 Months Ended	12 Months Ended
	Nov. 30, 2013	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Obligations of States and Political Subdivisions [Member]	Dec. 31, 2013 Obligations of States and Political Subdivisions [Member] General Obligation Bonds [Member]	Mar. 31, 2014 Special Revenue Bond [Member]	Dec. 31, 2013 Special Revenue Bond [Member]	Mar. 31, 2014 Education Bond [Member]	Dec. 31, 2013 Education Bond [Member]	Mar. 31, 2014 Water and Sewer Utility Bonds [Member]	Dec. 31, 2013 Water and Sewer Utility Bonds [Member]	Mar. 31, 2014 Equity Securities [Member] Securities	Mar. 31, 2014 Fixed Maturities [Member] Securities	Mar. 31, 2014 Accumulated Net Unrealized Investment Losses [Member]	Dec. 31, 2013 Accumulated Net Unrealized Investment Losses [Member]
Schedule of Investments [Line Items]
Aggregate fair value of bond held				$ 285.2	$ 294.1	$ 94.6	$ 91.9
Amortized cost of bond held				270.3	284.9	88.9	89.3
Percentage of which the company held security of any issuer		10.00%	10.00%
Percentage of investments in special revenue bonds								57.00%	56.00%	21.00%	23.00%
Net unrealized losses arising prior to reclassification date and classified in accumulated other comprehensive loss	15.1
Net unrealized losses reclassified in accumulated other comprehensive income														$ 14.7	$ 14.9
Depreciation of original cost value		20.00%
Time period for which individual security should be in unrealized position of twenty percentage or more to assume it as other than temporary decline		More than six months
Number of fixed maturity securities classified as available for sale												2	128
Percentage of ownership interest		48.20%