Investments - Schedule of Investments Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Investments available for sale
Amortized Cost	$ 4,836,528	$ 4,897,607
Unrealized Gains	10,678	98,747
Unrealized Losses	(184,301)	(33,467)
Fair Value	4,662,905	4,962,887
U.S. Treasury securities
Investments available for sale
Amortized Cost	437,450	447,926
Unrealized Gains	368	3,833
Unrealized Losses	(14,178)	(2,966)
Fair Value	423,640	448,793
U.S. agency securities
Investments available for sale
Amortized Cost		5,501
Unrealized Gains		3
Unrealized Losses		0
Fair Value		5,504
U.S. agency mortgage-backed securities
Investments available for sale
Amortized Cost	902,741	1,005,611
Unrealized Gains	689	13,365
Unrealized Losses	(48,655)	(10,113)
Fair Value	854,775	1,008,863
Municipal debt securities
Investments available for sale
Amortized Cost	530,839	598,764
Unrealized Gains	3,836	30,122
Unrealized Losses	(22,490)	(1,287)
Fair Value	512,185	627,599
Non-U.S. government securities
Investments available for sale
Amortized Cost	73,097	77,366
Unrealized Gains	1,411	3,232
Unrealized Losses	(2,765)	(855)
Fair Value	71,743	79,743
Corporate debt securities
Investments available for sale
Amortized Cost	1,339,172	1,428,645
Unrealized Gains	2,845	36,067
Unrealized Losses	(58,373)	(9,465)
Fair Value	1,283,644	1,455,247
Residential and commercial mortgage securities
Investments available for sale
Amortized Cost	565,116	541,638
Unrealized Gains	1,168	10,452
Unrealized Losses	(27,414)	(6,667)
Fair Value	538,870	545,423
Asset-backed securities
Investments available for sale
Amortized Cost	604,516	582,144
Unrealized Gains	361	1,673
Unrealized Losses	(10,426)	(2,114)
Fair Value	594,451	581,703
Money market funds
Investments available for sale
Amortized Cost	383,597	210,012
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	$ 383,597	$ 210,012

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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