Amortized Cost and Fair Value of Held to Maturity Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 21,704
Fair Value	21,704	112,446
Due in one year or less
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	21,704
Fair Value	21,704
Due in years one through two
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0
Fair Value	$ 0