Financial Instruments (Details) (USD $)	12 Months Ended
	Aug. 31, 2014	Aug. 31, 2013
Financial Instruments [Abstract]
Gain through other comprehensive income	$ 200,000
Financial Instruments [Line Items]
Amortized cost	1,728,015,000	1,823,409,000
Unrealized gains	280,000
Unrealized losses	(64,000)
Fair value	1,728,231,000
Cash and cash equivalents	1,452,948,000	1,673,659,000
Current marketable securities	187,472,000	105,809,000
Noncurrent marketable securities	87,811,000	43,941,000
Maximum [Member]
Financial Instruments [Line Items]
Contractual maturity held-to-maturity securities	3 years
Cash [Member]
Financial Instruments [Line Items]
Amortized cost	1,295,395,000	874,074,000
Unrealized gains	0
Unrealized losses	0
Unrealized gains		0
Unrealized losses		0
Fair value	1,295,395,000	874,074,000
Cash and cash equivalents	1,295,395,000	874,074,000
Current marketable securities	0	0
Noncurrent marketable securities	0	0
Money Market Funds [Member]
Financial Instruments [Line Items]
Amortized cost	132,508,000	732,530,000
Unrealized gains	0
Unrealized losses	0
Unrealized gains		0
Unrealized losses		0
Cash and cash equivalents	132,508,000	732,530,000
Current marketable securities	0	0
Noncurrent marketable securities	0	0
Tax-exempt municipal bonds [Member]
Financial Instruments [Line Items]
Amortized cost	106,543,000	95,746,000
Unrealized gains	155,000
Unrealized losses	(11,000)
Unrealized gains		19,000
Unrealized losses		(54,000)
Cash and cash equivalents	0	2,055,000
Current marketable securities	78,443,000	69,621,000
Noncurrent marketable securities	28,244,000	24,070,000
Corporate bonds [Member]
Financial Instruments [Line Items]
Amortized cost	106,575,000	38,428,000
Unrealized gains	123,000
Unrealized losses	(52,000)
Unrealized gains		6,000
Unrealized losses		(40,000)
Cash and cash equivalents	0	0
Current marketable securities	56,837,000	24,503,000
Noncurrent marketable securities	49,809,000	13,925,000
Time deposits [Member]
Financial Instruments [Line Items]
Amortized cost	50,100,000
Unrealized gains	0
Unrealized losses	0
Cash and cash equivalents	25,041,000
Current marketable securities	25,059,000
Noncurrent marketable securities	0
Commercial Paper [Member]
Financial Instruments [Line Items]
Amortized cost	11,793,000	9,828,000
Unrealized gains	1,000
Unrealized losses	0
Unrealized gains		0
Unrealized losses		0
Cash and cash equivalents	0	0
Current marketable securities	11,794,000	9,828,000
Noncurrent marketable securities	0	0
Other [Member]
Financial Instruments [Line Items]
Amortized cost	19,155,000	657,000
Unrealized gains	1,000
Unrealized losses	(1,000)
Unrealized gains		0
Unrealized losses		0
Cash and cash equivalents	4,000	0
Current marketable securities	15,339,000	657,000
Noncurrent marketable securities	3,812,000	0
Certificates of Deposit [Member]
Financial Instruments [Line Items]
Amortized cost		66,200,000
Unrealized gains		0
Unrealized losses		0
Cash and cash equivalents		65,000,000
Current marketable securities		1,200,000
Noncurrent marketable securities		0
Auction-rate securities [Member]
Financial Instruments [Line Items]
Amortized cost	5,946,000
Unrealized gains	0
Unrealized losses	0
Cash and cash equivalents	0	0
Current marketable securities	0	0
Noncurrent marketable securities	5,946,000	5,946,000
Level 1 [Member] | Money Market Funds [Member]
Financial Instruments [Line Items]
Fair value	132,508,000	732,530,000
Level 2 [Member] | Tax-exempt municipal bonds [Member]
Financial Instruments [Line Items]
Fair value	106,687,000
Fair value		95,711,000
Level 2 [Member] | Corporate bonds [Member]
Financial Instruments [Line Items]
Fair value	106,646,000
Fair value		38,394,000
Level 2 [Member] | Time deposits [Member]
Financial Instruments [Line Items]
Fair value	50,100,000
Level 2 [Member] | Commercial Paper [Member]
Financial Instruments [Line Items]
Fair value	11,794,000
Fair value		9,828,000
Level 2 [Member] | Other [Member]
Financial Instruments [Line Items]
Fair value	19,155,000
Fair value		657,000
Level 2 [Member] | Certificates of Deposit [Member]
Financial Instruments [Line Items]
Fair value		66,200,000
Level 3 [Member] | Auction-rate securities [Member]
Financial Instruments [Line Items]
Amortized cost		5,946,000
Fair value	$ 5,946,000