Employee Benefit Plans - Employee Stock Purchase Plan (Details) - Employee stock purchase plan 2008 - $ / shares shares in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Shares purchased (in shares)	1.4	1.4
Average exercise price per share (in dollars per share)	$ 19.75	$ 19.50

Number of shares issued during the period as a result of an employee stock purchase plan.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration