Gross Unrealized Gains and Losses (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	$ 17,984	$ 14,764
Gross unrealized losses	3,273	6,254
Municipal
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	561	258
Gross unrealized losses	560	813
Corporate
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	11,770	9,955
Gross unrealized losses	1,688	3,228
Foreign
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	862	363
Gross unrealized losses	873	2,142
U.S. Government
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	832	924
Gross unrealized losses	52	60
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	3,959	3,264
Gross unrealized losses	$ 100	$ 11