Tax Effects of Temporary Differences That Give Rise to Federal, Foreign, State and Local Deferred Tax Assets and Deferred Tax Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets:
Loss Reserve Discount	$ 20,425	$ 25,420
Unearned Premiums	24,352	33,886
Compensation Related	8,462	15,288
State and Local Net Deferred Tax Assets	616	699
Net Currency Translation Adjustments	2,084	5,363
Other	152	3,618
Total Gross Deferred Tax Assets	65,491	84,274
Less: Valuation Allowance	(1,798)	(699)
Total Deferred Tax Assets	63,693	83,575
Deferred Tax Liabilities:
Loss Reserve Discount - (Transition Rule)	(5,066)
Net Unrealized Gains/Losses on Securities	(8,708)	(10,142)
Deferred Acquisition Costs	(20,670)	(29,401)
Net Unrealized Foreign Exchange	(3,782)	(3,575)
Other	(3,196)	(4,048)
Total Deferred Tax Liabilities	(41,422)	(62,637)
Net Deferred Income Tax Asset (Liability)	22,271	20,938
Lloyd's
Deferred Tax Assets:
Lloyd's Year of Account Deferral	$ 9,400
Deferred Tax Liabilities:
Lloyd's Year of Account Deferral		$ (15,471)