Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 312,276	$ 315,012	$ 474,339	$ 484,971
Weighted average common shares outstanding - basic (in shares)	112,463	112,148	112,408	112,094
Net effect of dilutive securities:
Contingently issuable performance shares and restricted stock units (in shares)	283	385	331	405
Weighted average common shares outstanding — diluted (in shares)	112,746	112,533	112,739	112,499
Earnings per weighted-average common share outstanding
Net income attributable to common shareholders - basic (in dollars per share)	$ 2.78	$ 2.81	$ 4.22	$ 4.33
Net income attributable to common shareholders - diluted (in dollars per share)	$ 2.77	$ 2.80	$ 4.21	$ 4.31