Gross Unrealized Gains and Losses (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	$ 22,337	$ 14,764
Gross unrealized losses	2,021	6,254
Municipal
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	928	258
Gross unrealized losses	220	813
Corporate
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	13,939	9,955
Gross unrealized losses	855	3,228
Foreign
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	1,569	363
Gross unrealized losses	687	2,142
U.S. Government
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	743	924
Gross unrealized losses	31	60
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized gains	5,158	3,264
Gross unrealized losses	$ 228	$ 11