Percentage of financial targets to be achieved for participants to receive award.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Number of Employees

+ References

No definition available.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Unrecognized cost of unvested share-based compensation awards.

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

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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 equity-based payment instruments, excluding stock (or unit) options, that vested 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)(2)(iii)(2)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

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.

+ References

No definition available.

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Equity-Based Compensation - Restricted Stock Awards with Performance Conditions Additional Information (Details)		1 Months Ended		3 Months Ended		12 Months Ended
	Mar. 10, 2017 shares	Feb. 28, 2015 shares	Jan. 31, 2014 employee shares	Mar. 31, 2016 shares	Mar. 31, 2015 shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized equity-based compensation \| $						$ 16,733,000	$ 24,927,000	$ 40,115,000
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, granted (in shares)						555,680	581,672	3,239,948
Number of shares, vested (in shares)						766,159	785,820	299,703
Number of shares forfeited in period (in shares)						626,319	70,299	370,041
Unrecognized equity-based compensation \| $						$ 9,960,000	$ 18,946,000	$ 37,780,000
Restricted stock \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target bonus potentially payable in restricted stock								100.00%
Restricted stock \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target bonus potentially payable in restricted stock								150.00%
Performance metrics of GovDelivery \| Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, granted (in shares)			244,506
Number of employees granted shares in period \| employee			2
Number of shares, vested (in shares)				81,322	56,587
Number of shares forfeited in period (in shares)				62,937	43,660
Performance metrics of GovDelivery \| Restricted stock \| Vesting in first quarter of 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, granted (in shares)			100,247
Performance metrics of GovDelivery \| Restricted stock \| Vesting in second quarter of 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, granted (in shares)			144,259
2015 Performance based plan \| Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, granted (in shares)							316,715
Number of shares, vested (in shares)							175,249
Number of shares forfeited in period (in shares)							141,466
Percentage of target bonus potentially payable in restricted stock							150.00%
2015 Performance based plan \| Restricted stock \| Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, granted (in shares)		42,341
Number of shares, vested (in shares)				28,341
Number of shares forfeited in period (in shares)				14,000
2016 Performance based plan \| Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, granted (in shares)						419,283
Number of shares, vested (in shares)						251,570
Number of shares forfeited in period (in shares)						167,713
Percentage of target bonus potentially payable in restricted stock						100.00%
Share-based compensation expense \| $						$ 2,200,000	$ 4,100,000	$ 4,900,000
Unrecognized equity-based compensation \| $						$ 0
Subsequent Event \| 2017 Performance based plan \| Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares, granted (in shares)	263,756