Financial Instruments and Fair Value Measurements - Derivative Narrative (Details) $ in Thousands, £ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) derivative hybrid_instrument	Jun. 30, 2020 USD ($) derivative hybrid_instrument	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) derivative hybrid_instrument	Jun. 30, 2019 USD ($)	Feb. 29, 2020 USD ($) derivative	May 31, 2019 USD ($) derivative	May 31, 2019 GBP (£) derivative
Derivative [Line Items]
Number of hybrid debt instruments | hybrid_instrument	2	2		2
Interest expense
Derivative [Line Items]
Unrealized gains (losses) reclassified to income statement		$ (3,700)		$ (5,300)
Treasury rate locks | Cash flow hedge
Derivative [Line Items]
Number of derivative instruments | derivative						5
Number of instruments terminated | derivative	5
Aggregate notional amount						$ 500,000
Cross-currency swaps | Cash flow hedge
Derivative [Line Items]
Number of derivative instruments | derivative							4	4
Aggregate notional amount							$ 166,000	£ 130
Cross-currency swaps | Foreign exchange gains
Derivative [Line Items]
Unrealized gains (losses) reclassified to income statement		800	$ 1,400	12,200	$ 1,400
Cross-currency swap unrealized gains expected to be reclassified within next twelve months	$ 2,200	2,200		2,200
Interest rate swaps | Interest expense
Derivative [Line Items]
Unrealized gains (losses) reclassified to income statement			$ (454)		$ (1,100)
Interest rate swaps and treasury locks | Interest expense
Derivative [Line Items]
Interest rate swap unrealized loss expected to be reclassified within next twelve months	$ 11,700	$ 11,700		$ 11,700
Forward-Starting Swap [Member] | Cash flow hedge
Derivative [Line Items]
Number of derivative instruments | derivative	6	6		6
Aggregate notional amount	$ 500,000	$ 500,000		$ 500,000
Number of derivatives | derivative	4	4		4