Cash and Investments in Marketable Securities - Cash and Investments in Marketable Securities, Including Cash Equivalents and Restricted Cash (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	$ 129,452	$ 12,365	$ 32,443	$ 39,067
Short-term investments	171,353	225,459
Restricted cash	25,000	25,000
Total cash and investments in marketable securities	$ 325,805	$ 262,824

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References+ Details

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. For a classified balance sheet represents the current portion only (the noncurrent portion has a separate concept); there is a separate and distinct element for unclassified presentations.

+ References+ Details