Investments Held-to-Maturity Securities (Detail) (Corporate bonds, USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Short-term Investments
Schedule of Held-to-maturity Securities
Cost	$ 18,351	$ 8,182
Gross Unrealized Gains	234	78
Fair Value	18,585	8,260
Long Term Investments
Schedule of Held-to-maturity Securities
Cost	10,069	28,433
Gross Unrealized Gains	285	652
Gross Unrealized Losses		29
Fair Value	$ 10,354	$ 29,056