Derivative Instruments and Hedging Activities - Gains and losses on derivatives (Details) - Interest rate swaps - Hedging - Cash flow hedging - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Gains and losses on derivatives
Losses on derivative	$ 0.9		$ 1.6
Loss recorded in AOCL on derivatives, net	$ 8.5	$ 0.6	$ 11.6	$ 0.6

Amount, after tax and before reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118930883&loc=d3e637-108580

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