Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 550,559	$ 538,320	$ 511,047
Weighted Average common shares outstanding — basic (in shares)	112,666	112,443	112,129
Net effect of dilutive securities:
Contingently issuable performance shares and restricted stock units (in shares)	276	315	421
Weighted average common shares outstanding — diluted (in shares)	112,942	112,758	112,550
Earnings per weighted-average common share outstanding
Net income attributable to common shareholders - basic (in dollars per share)	$ 4.89	$ 4.79	$ 4.56
Net Income attributable to common shareholders - diluted (in dollars per share)	$ 4.87	$ 4.77	$ 4.54