Financial Instruments - Summary of Bond Activity (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Fair value at beginning of period	$ 30,011	$ 29,776
Purchases	9,695	5,650
Sales	(245)	(845)
Maturities and calls	(4,925)	(4,050)
Increase (decrease) in bond premium	1,000	(270)
Fair market value adjustment	27	(250)
Fair value at end of period	$ 35,563	$ 30,011