The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ References

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Number of options outstanding, including both vested and non-vested options.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Stock Based Compensation and Stock Options - Stock Options Outstanding and Exercisable (Detail) - $ / shares	6 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options	1,068,503	1,151,722	1,143,928	1,102,919	1,074,521	1,115,465
Weighted Average Remaining Contractual Life	3 years 4 months 13 days
Outstanding Options - Weighted Average Exercise Price	$ 35.28	$ 33.24	$ 32.02	$ 32.17	$ 31.56	$ 28.81
Exercisable Options - Number of Exercisable Options	451,320
Exercisable Options - Weighted Average Exercise Price	$ 30.42
Range of Exercise Price, $12.71 to $29.27 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	12.71
Range of Exercise Price, upper limit	$ 29.27
Number of Outstanding Options	217,809
Weighted Average Remaining Contractual Life	2 years 1 month 6 days
Outstanding Options - Weighted Average Exercise Price	$ 20.29
Exercisable Options - Number of Exercisable Options	217,809
Exercisable Options - Weighted Average Exercise Price	$ 20.29
Range of Exercise Price, $29.28 to $34.67 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	29.28
Range of Exercise Price, upper limit	$ 34.67
Number of Outstanding Options	215,769
Weighted Average Remaining Contractual Life	3 years 11 months 23 days
Outstanding Options - Weighted Average Exercise Price	$ 32.67
Exercisable Options - Number of Exercisable Options	36,344
Exercisable Options - Weighted Average Exercise Price	$ 33.83
Range of Exercise Price, $34.68 to $38.70 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	34.68
Range of Exercise Price, upper limit	$ 38.70
Number of Outstanding Options	242,022
Weighted Average Remaining Contractual Life	3 years 15 days
Outstanding Options - Weighted Average Exercise Price	$ 35.40
Exercisable Options - Number of Exercisable Options	56,847
Exercisable Options - Weighted Average Exercise Price	$ 34.98
Range of Exercise Price, $38.71 to $48.35 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	38.71
Range of Exercise Price, upper limit	$ 48.35
Number of Outstanding Options	392,903
Weighted Average Remaining Contractual Life	4 years 2 months 1 day
Outstanding Options - Weighted Average Exercise Price	$ 45.35
Exercisable Options - Number of Exercisable Options	140,320
Exercisable Options - Weighted Average Exercise Price	$ 21.71