Lloyd's Syndicate 1221 - Additional Information (Detail) (Lloyd's, Syndicate 1221) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Mar. 31, 2014 USD ($)	Jun. 30, 2014 GBP (£)	Jun. 30, 2013 GBP (£)	Jun. 30, 2014 USD ($)	Dec. 31, 2013	Dec. 31, 2012
Supplementary Insurance Information, by Segment [Line Items]
Syndicate 1221's stamp capacity		£ 215	£ 195
Percentage control of stamp capacity				100.00%	100.00%	100.00%
Pre-tax gain in connection with a change in functional currency	10.0
After-tax gain in connection with a change in functional currency	6.6
Letters of credit				153.2
Cash collateral posted				$ 1.0