Investments (Gross Unrealized Losses and Fair Value by Length of Time of Available-For-Sale Securities) (Detail) (Available-for-Sale Securities, USD $)	Dec. 31, 2014 Securities	Dec. 31, 2013 Securities
Schedule Of Available For Sale Securities [Line Items]
Number of securities	37	58
Fair Value	$ 253,226,000	$ 321,936,000
Less than 12 months	122,000	15,243,000
More than 12 months	5,748,000	415,000
Total Unrealized Losses	5,870,000	15,658,000
U.S. Government Agencies
Schedule Of Available For Sale Securities [Line Items]
Number of securities	14	15
Fair Value	141,679,000	139,466,000
Less than 12 months	60,000	8,222,000
More than 12 months	2,758,000	0
Total Unrealized Losses	2,818,000	8,222,000
State and municipal
Schedule Of Available For Sale Securities [Line Items]
Number of securities	2	12
Fair Value	1,409,000	11,680,000
Less than 12 months	4,000	156,000
More than 12 months	0	0
Total Unrealized Losses	4,000	156,000
Mortgage-Backed
Schedule Of Available For Sale Securities [Line Items]
Number of securities	20	30
Fair Value	108,902,000	169,377,000
Less than 12 months	58,000	6,865,000
More than 12 months	2,878,000	127,000
Total Unrealized Losses	2,936,000	6,992,000
Trust Preferred
Schedule Of Available For Sale Securities [Line Items]
Number of securities	1	1
Fair Value	1,236,000	1,413,000
Less than 12 months	0	0
More than 12 months	112,000	288,000
Total Unrealized Losses	$ 112,000	$ 288,000