Summary of Significant Accounting Policies and Procedures and Newly Adopted Accounting Standards - Derivative and Hedging Activities (Details) £ in Millions	1 Months Ended			12 Months Ended
	Dec. 31, 2020 USD ($)	Jul. 31, 2020 USD ($) derivative	Jun. 30, 2020 USD ($) derivative	Dec. 31, 2020 USD ($)	Dec. 31, 2020 GBP (£) derivative hybrid_instrument mortgage	Dec. 31, 2020 USD ($) derivative hybrid_instrument mortgage	Feb. 29, 2020 USD ($) derivative	Dec. 31, 2019 USD ($)	May 31, 2019 GBP (£) derivative	May 31, 2019 USD ($) derivative	Oct. 31, 2018 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Swap exchange notional amount						$ 1,541,400,000		$ 673,400,000
Number of hybrid debt instruments | hybrid_instrument					2	2
Term loans | $250 million senior unsecured term loan due Mar 2024
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Face amount of loan						$ 250,000,000.0		250,000,000.0			$ 250,000,000.0
Notes payable | 0.750% notes, issued in December 2020 and due in March 2026
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Face amount of loan						$ 325,000,000.0
Interest rate (as a percent)					0.75%	0.75%
Notional amount applied to notes payable	$ 100,000,000.0
Notes payable | 1.800% notes, issued in December 2020 and due in March 2033
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Face amount of loan						$ 400,000,000.0
Interest rate (as a percent)					1.80%	1.80%
Interest rate swap, maturity Mar 2024
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of derivative instruments | derivative					1	1
Currency exchange swap | Not designated as hedging instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Swap exchange notional amount					£ 463.1	$ 625,000,000.0		$ 0
Net loss from derivative				$ 14,500,000
Treasury rate locks | Cash flow hedge
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of derivative instruments | derivative							5
Swap exchange notional amount							$ 500,000,000.0
Number of instruments terminated | derivative			5
Forward starting swaps | Cash flow hedge
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of derivative instruments | derivative			6		6	6
Swap exchange notional amount			$ 500,000,000.0
Number of derivative instruments | derivative					4	4
Redesignated forward starting swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Swap exchange notional amount		$ 350,000,000.0
Redesignated forward starting swaps | Cash flow hedge
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of derivative instruments | derivative					4	4
Swap exchange notional amount						$ 350,000,000.0
Number of instruments being amortized | derivative		4
Other forward starting swaps | Cash flow hedge
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of derivative instruments | mortgage					2	2
Swap exchange notional amount						$ 150,000,000.0
Cross-currency swaps | Cash flow hedge
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of derivative instruments | derivative									4	4
Swap exchange notional amount									£ 130.0	$ 166,000,000