Fair value of financial instruments (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	$ 191,685	$ 199,468
Accretion of premium on short-term investments	4,424	4,598	2,630
Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	165,898	192,548
Short-term investments | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value		1,000
Short-term investments | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	1,003	2,750
Short-term investments | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	148,993	160,241
Short-term investments | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	3,391	3,465
Short-term investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	12,511	25,092
Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	168,139	198,038
Total | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	165,898	192,548
Total | Short-term investments | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value		1,000
Total | Short-term investments | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	1,003	2,750
Total | Short-term investments | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	148,993	160,241
Total | Short-term investments | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	3,391	3,465
Total | Short-term investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	12,511	25,092
Total | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	2,241	5,490
Total | Cash equivalents | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	2,241	4,490
Total | Cash equivalents | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value		1,000
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	2,241	4,490
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	2,241	4,490
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash equivalents | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	2,241	4,490
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash equivalents | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value		0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	165,898	193,548
Significant Other Observable Inputs (Level 2) | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	165,898	192,548
Significant Other Observable Inputs (Level 2) | Short-term investments | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value		1,000
Significant Other Observable Inputs (Level 2) | Short-term investments | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	1,003	2,750
Significant Other Observable Inputs (Level 2) | Short-term investments | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	148,993	160,241
Significant Other Observable Inputs (Level 2) | Short-term investments | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	3,391	3,465
Significant Other Observable Inputs (Level 2) | Short-term investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	12,511	25,092
Significant Other Observable Inputs (Level 2) | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	1,000
Significant Other Observable Inputs (Level 2) | Cash equivalents | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Significant Other Observable Inputs (Level 2) | Cash equivalents | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value		1,000
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Short-term investments | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value		0
Significant Unobservable Inputs (Level 3) | Short-term investments | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Short-term investments | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Short-term investments | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Short-term investments | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Cash equivalents | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Cash equivalents | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value		$ 0