Fair Value Measurements and Derivative Instruments (Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	$ 349,587	$ 325,794
Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	289,963	508,019
Equity securities	28,100	26,583
Mortgage-backed / asset-backed securities	231,863	220,678
Total assets	693,459	885,413
Liabilities	(786)	(4,123)
Level 1 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	39,573	73,228
Equity securities	0	0
Mortgage-backed / asset-backed securities	0	0
Total assets	67,499	91,726
Liabilities	0	0
Level 2 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	250,390	434,791
Equity securities	28,100	26,583
Mortgage-backed / asset-backed securities	231,863	220,678
Total assets	625,960	793,687
Liabilities	(786)	(4,123)
Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
Equity securities	0	0
Mortgage-backed / asset-backed securities	0	0
Total assets	0	0
Liabilities	0	0
Interest rate swaps | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	4,117
Derivative liabilities		(2,163)
Interest rate swaps | Level 1 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0
Derivative liabilities		0
Interest rate swaps | Level 2 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	4,117
Derivative liabilities		(2,163)
Interest rate swaps | Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0
Derivative liabilities		0
Foreign exchange contracts | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	1,117	3,776
Derivative liabilities	(786)	(1,960)
Foreign exchange contracts | Level 1 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Foreign exchange contracts | Level 2 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	1,117	3,776
Derivative liabilities	(786)	(1,960)
Foreign exchange contracts | Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Commingled fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	1,698	1,722
Commingled fixed income securities | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	20,725	21,391
Commingled fixed income securities | Level 1 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	1,698	1,722
Commingled fixed income securities | Level 2 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	19,027	19,669
Commingled fixed income securities | Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Government and related securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	50,076	31,961
Government and related securities | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	51,624	33,533
Government and related securities | Level 1 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	26,228	16,776
Government and related securities | Level 2 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	25,396	16,757
Government and related securities | Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	65,950	71,433
Corporate debt securities | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	65,950	71,433
Corporate debt securities | Level 1 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Corporate debt securities | Level 2 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	65,950	71,433
Corporate debt securities | Level 3 | Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	$ 0	$ 0