Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Income	$ 190,055	$ 307,283	$ 179,261	$ 184,665	$ 259,695	$ 98,655	$ 676,600	$ 543,015
Participating Securities, Distributed and Undistributed Earnings (Loss), Basic	(1,019)			0			(3,764)	0
Net Income (Loss) Available to Common Stockholders, Basic	$ 189,036			$ 184,665			$ 672,836	$ 543,015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Anti-dilutive stock options excluded from diluted earnings per share computations (in shares)	33			0			33	0
Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights	213						223
Weighted average shares outstanding: [Abstract]
Basic (in shares)	39,214			40,101			39,599	40,146
Effect of dilutive securities: [Abstract]
Stock options and employee stock purchase plan (in shares)	366			590			413	620
Diluted (in shares)	39,580			40,691			40,012	40,766
Earnings Per Share, Basic [Abstract]
Basic (in dollars per share)	$ 4.82			$ 4.60			$ 16.99	$ 13.53
Earnings Per Share, Basic and Diluted [Abstract]
Diluted (in dollars per share)	$ 4.78			$ 4.54			$ 16.82	$ 13.32