Investments - Schedule of Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Held-to-maturity Securities [Line Items]
Short-Term	$ 6,035	$ 6,457
Long-Term	64,082	57,511
Municipal Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Short-Term	5,539	5,492
Long-Term	35,827	34,495
Federal Home Loan Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Long-Term	27,030	22,520
Certificates of Deposit [Member]
Schedule of Held-to-maturity Securities [Line Items]
Short-Term	496	965
Long-Term	$ 1,225	$ 496