Cash, Cash Equivalents, and Investments - Effective Maturity Dates of Available-for-Sale Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	$ 184,822
1-2 Years	105,079
2-3 Years	117,581
3-4 Years	5,039
Fair Value	412,521
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	109,040
1-2 Years	64,080
2-3 Years	42,686
3-4 Years	3,143
Fair Value	218,949
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	53,559
1-2 Years	14,917
2-3 Years	6,903
Fair Value	75,379
Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
1-2 Years	16,003
2-3 Years	57,663
Fair Value	73,666
Sovereign Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	11,448
1-2 Years	8,810
2-3 Years	7,575
Fair Value	27,833
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	9,276
1-2 Years	1,269
2-3 Years	2,754
3-4 Years	1,896
Fair Value	15,195
Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	1,499
Fair Value	$ 1,499