Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes the cost of other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include Short-Term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For 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. Also includes the cost of short-term investments, exclusive of cash equivalents, are marketable securities intended to be sold within one year (or the normal operating cycle if longer) and include trading securities, available-for-sale securities, and held-to-maturity securities (if maturing within one year).

No definition available.

Cash and Cash Equivalents and Investments - Cash and Cash Equivalents and Investments from Continuing Operations (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Cash, Cost	$ 136,784	$ 157,317
Cash
Money market funds, Cost	103,764	122,827
Money market funds, Gross Unrealized Gain	12	448
Cash and cash equivalents, unrestricted, Cost	240,548	280,144
Cash and cash equivalents, unrestricted, gain	12	448
Total cash and cash equivalents, Gross Unrealized Gain	12
Total short-term investments (available-for-sale), Gross Unrealized Gain	4	31
Total cash and cash equivalents and short-term investments, Gross Unrealized Gain	16	479
Cash, Gross Unrealized (Loss)
Money market funds, Gross Unrealized (Loss)
Total cash and cash equivalents, Gross Unrealized (Loss)
Total short-term investments (available-for-sale), Gross Unrealized (Loss)	(7)	(34)
Total cash and cash equivalents and short-term investments, Gross Unrealized (Loss)	(7)	(34)
Cash, Fair Value	136,784	157,317
Money market funds, Fair Value	103,776	123,275
Cash and cash equivalents, unrestricted, Fair Value	240,560	280,592	260,638	258,244
Restricted cash	97,878	0
Total cash and cash equivalents, Cost	338,426
Total cash and cash equivalents, Fair Value	338,438
Long-term investments (available-for-sale), Fair Value	71,258	171,022
Total short-term investments (available-for-sale)	63,879	160,610
Total short-term investments (available-for-sale), Fair Value	63,876	160,607
Total cash and cash equivalents and short-term investments	402,305	440,754
Total cash and cash equivalents and short-term investments	402,314	441,199
US Treasury Bill [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Short-term investments (available-for-sale), Gross Unrealized Gain	4	31
Short-term investments (available-for-sale), Gross Unrealized (Loss)	(7)	(5)
Short-term investments (available-for-sale), Cost	63,879	133,648
Long-term investments (available-for-sale), Fair Value	63,876	133,674
Municipal Bonds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Long-term investments (available-for-sale), Gross Unrealized Gain
Long-term investments (available-for-sale), Gross Unrealized (Loss)	(468)	(735)
Long-term investments (available-for-sale), Fair Value	7,382	10,415
Long-term investments (available-for-sale), Cost	7,850	11,150
Total investments at fair value	7,382	10,415
U.S. Government Agencies [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Short-term investments (available-for-sale), Gross Unrealized (Loss)		(29)
Short-term investments (available-for-sale), Cost		26,962
Long-term investments (available-for-sale), Fair Value		$ 26,933