Fair Value Measurements (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Assets
Total assets	$ 3,202,422	$ 2,953,100
Accrued liabilities
Derivative liabilities	17,472	13,447
Total liabilities	$ 17,472	13,447
Fair value assumptions, expected term	3 years 11 months 1 day
Level 1 [Member]
Assets
Total assets	$ 1,494,093	1,175,927
Level 2 [Member]
Assets
Total assets	1,708,329	1,777,173
Accrued liabilities
Total liabilities	1,372	1,847
Level 3 [Member]
Accrued liabilities
Total liabilities	16,100	11,600
Foreign currency derivative contracts [Member]
Accrued liabilities
Accrued liabilities	1,372	1,847
Foreign currency derivative contracts [Member] | Level 2 [Member]
Accrued liabilities
Accrued liabilities	1,372	1,847
Other derivative financial instrument [Member]
Accrued liabilities
Derivative liabilities	16,100	11,600
Other derivative financial instrument [Member] | Level 3 [Member]
Accrued liabilities
Derivative liabilities	16,100	11,600
Money market funds [Member]
Assets
Cash equivalents	419,858	276,898
Money market funds [Member] | Level 1 [Member]
Assets
Cash equivalents	419,858	276,898
Commercial paper [Member]
Assets
Cash equivalents		12,049
Short-term investments	26,662	55,374
Commercial paper [Member] | Level 2 [Member]
Assets
Cash equivalents		12,049
Short-term investments	26,662	55,374
Certificates of deposit [Member]
Assets
Short-term investments	10,005
Certificates of deposit [Member] | Level 2 [Member]
Assets
Short-term investments	10,005
U.S. treasury securities [Member]
Assets
Cash equivalents	130,313	25,000
Short-term investments	943,922	874,029
U.S. treasury securities [Member] | Level 1 [Member]
Assets
Cash equivalents	130,313	25,000
Short-term investments	943,922	874,029
U.S. agency securities [Member]
Assets
Cash equivalents	37,349	51,500
Short-term investments	446,510	606,202
U.S. agency securities [Member] | Level 2 [Member]
Assets
Cash equivalents	37,349	51,500
Short-term investments	446,510	606,202
Corporate debt securities [Member]
Assets
Short-term investments	1,156,598	1,026,898
Corporate debt securities [Member] | Level 2 [Member]
Assets
Short-term investments	1,156,598	1,026,898
Municipal securities [Member]
Assets
Short-term investments	8,012	10,642
Municipal securities [Member] | Level 2 [Member]
Assets
Short-term investments	8,012	10,642
Foreign currency derivative contracts [Member]
Assets
Other current assets	23,193	14,508
Foreign currency derivative contracts [Member] | Level 2 [Member]
Assets
Other current assets	$ 23,193	$ 14,508