Fair Value Measurements - Changes in Level 3 Assets Measured at Estimated Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation Calculation [Roll Forward]
Balance at the beginning of the year	$ 10,779	$ 13,225
Purchases, issuances and settlements	20,499	1,376
Sales	(251)	(6,050)
Gains included in earnings	234	4,606
Total unrealized gains/(losses)	741	(2,378)
Balance at the end of the year	$ 32,002	$ 10,779