Cash, Cash Equivalents and Investments - Effective Maturity Dates of Available-for-Sale Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	$ 90,456
1-2 Years	188,648
2-3 Years	135,880
3-4 Years	43,533
4-5 Years	25,384
5-8 Years	5,444
Fair Value, Total	489,345
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	30,889
1-2 Years	82,238
2-3 Years	97,921
3-4 Years	19,718
4-5 Years	16,417
5-8 Years	0
Fair Value, Total	247,183
Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	0
1-2 Years	85,629
2-3 Years	4,783
3-4 Years	0
4-5 Years	0
5-8 Years	0
Fair Value, Total	90,412
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	1,311
1-2 Years	4,788
2-3 Years	19,542
3-4 Years	23,815
4-5 Years	8,967
5-8 Years	5,444
Fair Value, Total	63,867
Euro liquidity fund [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	48,235
1-2 Years	0
2-3 Years	0
3-4 Years	0
4-5 Years	0
5-8 Years	0
Fair Value, Total	48,235
Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	6,883
1-2 Years	4,506
2-3 Years	5,060
3-4 Years	0
4-5 Years	0
5-8 Years	0
Fair Value, Total	16,449
Sovereign Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	0
1-2 Years	9,768
2-3 Years	3,693
3-4 Years	0
4-5 Years	0
5-8 Years	0
Fair Value, Total	13,461
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	1,237
1-2 Years	1,719
2-3 Years	4,881
3-4 Years	0
4-5 Years	0
5-8 Years	0
Fair Value, Total	7,837
Supranational bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 1 Year	1,901
1-2 Years	0
2-3 Years	0
3-4 Years	0
4-5 Years	0
5-8 Years	0
Fair Value, Total	$ 1,901