Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Level 3 Inputs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Other assets and (liabilities)
Total realized and unrealized gains (losses)
Amounts acquired	$ 19,970
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	46,186	$ (2,952)
Total realized and unrealized gains (losses)
Total foreign exchange gains	5
Purchases	13,405	45,254
Settlements	20	983
Amounts acquired	19,970
Ending balance	79,365	46,186
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Other income (loss)
Total realized and unrealized gains (losses)
Included in other income	(221)	2,901
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	54,545	0
Total realized and unrealized gains (losses)
Total foreign exchange gains	5
Purchases	17,958	54,545
Settlements	0	0
Amounts acquired	0
Ending balance	74,634	54,545
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Other investments | Other income (loss)
Total realized and unrealized gains (losses)
Included in other income	2,126	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Other assets and (liabilities)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(8,359)	(2,952)
Total realized and unrealized gains (losses)
Total foreign exchange gains	0
Purchases	(4,553)	(9,291)
Settlements	20	983
Ending balance	4,731	(8,359)
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Other assets and (liabilities) | Other income (loss)
Total realized and unrealized gains (losses)
Included in other income	$ (2,347)	$ 2,901