Equity - Unconsolidated Affiliates (Details) $ in Millions	Sep. 30, 2017 USD ($) affiliate	Dec. 31, 2016 USD ($) affiliate
Equity [Abstract]
Number of unconsolidated affiliates with an interest rate swap \| affiliate	1	1
Unconsolidated affiliate's interest rate swap liability, fair value	$ 30.1	$ 33.1
Equity method investments ownership percentage	50.00%	50.00%
Proportionate share in unconsolidated affiliate's interest rate swap liability	$ 15.1	$ 16.5

Represents the entity's proportionate share of the interest rate swap liability of an equity method investee.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value as of the balance sheet date of interest rate derivative liabilities reported by an equity method investment of the entity.

+ References

No definition available.

+ Details

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Namespace Prefix:	dst_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Represents the number of unconsolidated affiliates of the entity having an interest rate swap liability.

+ References

No definition available.

+ Details

Name:	dst_NumberOfUnconsolidatedAffiliatesOfEntityHavingInterestRateSwapLiability
Namespace Prefix:	dst_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_EquityAbstract
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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

+ Details

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Balance Type:	na
Period Type:	instant