Marketable Securities Summary of Marketable Securities Including Accrued Interest Receivable (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 6,124	$ 133,263
Gross Unrealized Gains	2	102
Gross Unrealized Losses	(1)	(57)
Fair Value	6,125	133,308
U.S. Treasury securities and obligations of U.S. government agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		30,343
Gross Unrealized Gains		39
Gross Unrealized Losses		0
Fair Value		30,382
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,283	54,725
Gross Unrealized Gains	0	13
Gross Unrealized Losses	0	(48)
Fair Value	2,283	54,690
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		857
Gross Unrealized Gains		27
Gross Unrealized Losses		0
Fair Value		884
Other debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	66	5,056
Gross Unrealized Gains	0	3
Gross Unrealized Losses	0	0
Fair Value	66	5,059
Municipal securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,775	30,258
Gross Unrealized Gains	2	18
Gross Unrealized Losses	(1)	(9)
Fair Value	$ 3,776	30,267
Bank certificate of deposits
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		12,024
Gross Unrealized Gains		2
Gross Unrealized Losses		0
Fair Value		$ 12,026

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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