Fair Value measurement - Schedule of Long-term Restricted Certificates of Deposit (Detail) (Restricted Certificates of Deposit [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2014 Security	Dec. 31, 2013
Restricted Certificates of Deposit [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cost	$ 20,943	$ 12,789
Gross Unrealized Gains	0	0
Recorded Basis	$ 20,943	$ 12,789
Fair Value Category	2

- Definition

A savings certificate entitling the Entity (that is, bearer) to receive interest at an established maturity date, based upon a fixed interest rate. A certificate of deposit may be issued in any denomination. Certificates of deposit are generally issued by commercial banks and, therefore, insured by the FDIC (up to the prescribed limit). Certificates of deposit generally restrict holders from withdrawing funds on demand without the incurrence of penalties. Generally, only certificates of deposit with original maturities of three months or less qualify as cash equivalents. Original maturity means original maturity to the entity holding the investment. As a related example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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