Insurance Activity - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Aug. 31, 2009
Effects of Reinsurance [Line Items]
Quoted percentage to share base				50.00%
Balances in the fair market reserve	$ 16.0		$ 46.3
Decreased value of fair market reserve	30.3	1.0
Decrease in expense	30.3	1.0
United Guaranty [Member]
Effects of Reinsurance [Line Items]
Amount paid by UGRIC	17.7
WMMRC [Member]
Effects of Reinsurance [Line Items]
Amount paid by UGRIC	$ 65.4
Second loss layer risk percentage of range minimum				5.00%
Second loss layer risk percentage of range maximum				10.00%
First loss layer risk percentage of range minimum				4.00%
First loss layer risk percentage of range maximum				5.00%
Minimum period of reinsurance agreements	5 years
Maximum period of reinsurance agreements	10 years
WMMRC [Member] \| Minimum [Member]
Effects of Reinsurance [Line Items]
Net of ceding commission, percentage				25.00%
WMMRC [Member] \| Maximum [Member]
Effects of Reinsurance [Line Items]
Net of ceding commission, percentage				40.00%