Amortized Cost and Fair Value of Held to Maturity Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 106,441
Fair Value	106,575	112,446
Due in one year or less
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	67,460
Fair Value	67,527
Due in years one through two
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	38,981
Fair Value	$ 39,048