Fair Value Measurement of Assets and Liabilities - Changes in Level 3 Assets Measured at Fair Value on Recurring Basis (Detail) (Available for sale securities [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Available for sale securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of the period	$ 71,674	$ 77,311
Total net (losses) gains for the period included in, Net income		(5,247)
Total net gains (losses) for the period included in, Other comprehensive income	657	18,482
Sales	(36,681)	(9,146)
Settlements	(7,127)	(9,726)
Balance, end of the period	28,523	71,674
Change in unrealized losses for the period included in earnings for assets held at the end of the reporting period		$ (5,247)