Common Stock (Details) - USD ($)	3 Months Ended		9 Months Ended		240 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Oct. 26, 2021	Dec. 31, 2020
Equity, Class of Treasury Stock [Line Items]
Common stock, outstanding	53,382,560		53,382,560		53,382,560		54,755,900
Common stock, issued	18,528	24,694	145,815	186,544
Common stock, dividend, per share			$ 0.13
Number of shares repurchased			1,500,000		19,100,000
Stock repurchased (in US dollars)	$ 45,217,000		$ 183,247,000	$ 99,048,000	$ 1,090,000,000.00
Remaining authorized repurchase amount (in US dollars)	62,700,000		62,700,000		62,700,000
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Stock repurchase, authorized amount (in US dollars)						$ 300,000,000
RepurchaseProgramSep2011toSep2021
Equity, Class of Treasury Stock [Line Items]
Stock repurchase, authorized amount (in US dollars)	$ 1,150,000,000		$ 1,150,000,000		$ 1,150,000,000