Revenue from Contracts with Customers (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Deferred revenue recognized in period related to beginning balance	$ 281.7
Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Percentage of Revenue	73.00%	80.00%
Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Percentage of Revenue	27.00%	20.00%
U.S. [Member]
Disaggregation of Revenue [Line Items]
Percentage of Revenue	76.00%	76.00%
Non U.S. [Member]
Disaggregation of Revenue [Line Items]
Percentage of Revenue	24.00%	24.00%
Kaplan International [Member]
Disaggregation of Revenue [Line Items]
Contract with Customer, Asset, Net, Noncurrent	$ 5.3
Kaplan International [Member] \| Long-term Contract with Customer [Member]
Disaggregation of Revenue [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 11.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	2 years
Test Preparation [Member] \| Long-term Contract with Customer [Member]
Disaggregation of Revenue [Line Items]
Minimum Term of Contract	12 months
Revenue, Remaining Performance Obligation, Amount	$ 8.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months
Revenue Remaining Performance Obligation Percentage of Revenue Expected to be Recognized Over Next 12 Months	66.00%

Minimum Term of Contract

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- Definition

Percentage of Revenue Recognized During Period from Contract with Customer, Excluding Assessed Tax

+ References

No definition available.

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- Definition

Revenue Remaining Performance Obligation Percentage of Revenue Expected to be Recognized Over Next 12 Months

+ References

No definition available.

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- Definition

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as noncurrent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=118944033&loc=SL49130533-203044

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130549-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118944033&loc=SL49130531-203044

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- Definition

Amount of revenue recognized that was previously reported as deferred or unearned revenue.

+ References

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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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- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130556-203045

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- Definition

Period in which remaining performance obligation is expected to be recognized as revenue, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130556-203045

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