Financial Instruments and Fair Value Disclosures - Assets and Liabilities Measured at Fair Value on Recurring and Nonrecurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Measurements, Nonrecurring [Member]
Assets:
Assets held for sale	$ 3,900	$ 3,900
Fair Value Measurements, Recurring [Member]
Assets:
Short-term investments	1,205,626	1,434,751
FOREX contracts	3,272	3,627
Mortgage-backed securities	224	301
Total assets	1,209,122	1,438,679
Liabilities:
FOREX contracts	(4,304)	(29)
Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets:
Assets held for sale
Level 1 [Member] | Fair Value Measurements, Recurring [Member]
Assets:
Short-term investments	1,205,626	1,434,751
FOREX contracts
Mortgage-backed securities
Total assets	1,205,626	1,434,751
Liabilities:
FOREX contracts
Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets:
Assets held for sale
Level 2 [Member] | Fair Value Measurements, Recurring [Member]
Assets:
Short-term investments
FOREX contracts	3,272	3,627
Mortgage-backed securities	224	301
Total assets	3,496	3,928
Liabilities:
FOREX contracts	(4,304)	(29)
Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets:
Assets held for sale	3,900	3,900
Level 3 [Member] | Fair Value Measurements, Recurring [Member]
Assets:
Short-term investments
FOREX contracts
Mortgage-backed securities
Total assets
Liabilities:
FOREX contracts