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Stock-Based Compensation - Schedule of Restricted Stock Unit Programs Outstanding (Detail) | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Equity Classified RSUs [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of options outstanding, Beginning Balance | 367,726 | 181,732 | 184,084
Granted | 320,131 | 208,458 | 20,940
Dividend equivalents | 1,895 | 2,022 | 946
Redeemed | (84,322) | (24,486) | (24,238)
Number of options outstanding, Ending Balance | 605,430 | 367,726 | 181,732
Liability Classified RSUs [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of options outstanding, Beginning Balance | 29,806 | 34,242 | 12,272
Granted | 15,364 | 4,150 | 26,000
Dividend equivalents | 1,133 | 946 | 391
Redeemed | (26,204) | (9,532) | (4,421)
Number of options outstanding, Ending Balance | 20,099 | 29,806 | 34,242
Liability Classified DSUs [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of options outstanding, Beginning Balance | 198,446 | 186,348 | 153,013
Granted | 37,456 | 22,669 | 40,954
Dividend equivalents | 5,145 | 4,696 | 1,758
Redeemed | (34,124) | (15,267) | (9,377)
Number of options outstanding, Ending Balance | 206,923 | 198,446 | 186,348
Release of restricted stock units [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of options outstanding, Beginning Balance | 595,978 | 402,322 | 349,369
Granted | 372,951 | 235,277 | 87,894
Dividend equivalents | 8,173 | 7,664 | 3,095
Redeemed | (144,650) | (49,285) | (38,036)
Number of options outstanding, Ending Balance | 832,452 | 595,978 | 402,322

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- Definition Share based compensation arrangement by share based payment award equity instruments other than options dividend equivalents in period. + References No definition available. + Details
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- Definition Share based compensation arrangement by share based payment award equity instruments other than options redeemed in period. + References No definition available. + Details
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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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(2)(c) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(2)(b) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(2)(a) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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