Business Acquisitions - Transactions (Details) $ / shares in Units, $ in Thousands				3 Months Ended
	Jan. 04, 2021 USD ($)	Oct. 30, 2020 USD ($) $ / shares shares	Jul. 01, 2020 USD ($) shares	Mar. 31, 2021 USD ($) shares	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Business acquisition
Cash paid for acquisition, net				$ 55,921	$ 9,000
Goodwill				14,451,975		$ 14,581,255	$ 746,079
Income tax expense				87,039	$ (711)
Consultant Connect
Business acquisition
Total consideration	$ 56,300
Cash paid for acquisition, net				55,900
Goodwill	47,300
Consultant Connect | Client relationships
Business acquisition
Finite-lived intangibles	9,800
Consultant Connect | Technology
Business acquisition
Finite-lived intangibles	1,900
Consultant Connect | Brand
Business acquisition
Finite-lived intangibles	$ 600
Livongo Health
Business acquisition
Merger, conversion of common shares ratio		0.5920
Merger, conversion price (in dollars per share) | $ / shares		$ 4.24
Merger, special cash dividend | $ / shares		$ 7.09
Initial consideration		$ 13,938,000
Total consideration				13,876,900
Initial cash consideration		401,000
Cash paid for acquisition, net				380,200
Debt incurred upon acquisition				$ 555,400
Amount related to conversion feature of the Livongo Notes guaranteed by the Company		$ 555,400
Initial equity consideration (in shares) | shares		60,400,000
Initial equity consideration		$ 12,981,600
Equity consideration (in shares) | shares				60,200,000
Equity consideration				$ 12,941,300
Acquisition related costs		59,000
Excess shares identified | shares				205,279
Excess shares not withheld | shares				85,481
Merger-related cash payments identified as cash overpayments				$ 5,600
Excess shares cancelled | shares				205,279
Increase to receivables				$ 20,800
Decrease to stockholders' equity				(40,300)
Decrease to goodwill				$ (61,100)
Goodwill		12,744,580
Livongo Health | Client relationships
Business acquisition
Finite-lived intangibles		1,050,000
Livongo Health | Technology
Business acquisition
Finite-lived intangibles		$ 300,000
InTouch
Business acquisition
Initial consideration			$ 1,078,500
Initial cash consideration			160,700
Cash acquired			$ 1,100
Initial equity consideration (in shares) | shares			4,600,000
Initial equity consideration			$ 918,800
Acquisition related costs			12,500
Goodwill			899,978
InTouch | Client relationships
Business acquisition
Finite-lived intangibles			164,580
InTouch | Technology
Business acquisition
Finite-lived intangibles			$ 29,190