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Stock-Based Compensation - Schedule of Restricted Stock Unit Programs Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Equity Classified RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options outstanding, Beginning Balance	985,278	1,263,709
Granted	356,422	363,053
Dividend equivalents	1,633	1,678
Redeemed	(495,627)	(643,162)
Number of options outstanding, Ending Balance	847,706	985,278
Liability Classified RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options outstanding, Beginning Balance	46,052	60,238
Granted	15,922	18,050
Dividend equivalents	1,094	1,132
Forfeitures		(820)
Redeemed	(28,236)	(32,548)
Number of options outstanding, Ending Balance	34,832	46,052
Liability/Equity Classified DSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options outstanding, Beginning Balance	303,261	254,894
Granted	43,955	44,272
Dividend equivalents	5,468	4,095
Number of options outstanding, Ending Balance	352,684	303,261
Release of Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options outstanding, Beginning Balance	1,334,591	1,578,841
Granted	416,299	425,375
Dividend equivalents	8,195	6,905
Forfeitures		(820)
Redeemed	(523,863)	(675,710)
Number of options outstanding, Ending Balance	1,235,222	1,334,591

X

- Definition

Share based compensation arrangement by share based payment award equity instruments other than options dividend equivalents in period.

+ References

No definition available.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options redeemed in period.

+ References

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

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)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

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)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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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