Earnings per Share Earnings per Share (EPS Calculations) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Calculation of basic EPS:
Net income	$ 149,059	$ 138,216	$ 127,184	$ 127,126	$ 112,350	$ 96,894	$ 414,459	$ 336,370
Less: Net income allocated to participating securities	(103)			(152)			(253)	(406)
Net income attributable to common shareholders	$ 148,956			$ 126,974			$ 414,206	$ 335,964
Weighted-average common shares outstanding (in shares)	235,267,000			218,042,000			233,773,000	216,140,000
Basic EPS (in dollars per share)	$ 0.63			$ 0.58			$ 1.77	$ 1.55
Calculation of diluted EPS:
Net income	$ 149,059	$ 138,216	$ 127,184	$ 127,126	$ 112,350	$ 96,894	$ 414,459	$ 336,370
Diluted weighted-average common shares outstanding (in shares)	236,153,000			218,847,000			234,585,000	216,912,000
Diluted EPS (in dollars per share)	$ 0.63			$ 0.58			$ 1.77	$ 1.55
Anti-dilutive securities, options to purchase common stock outstanding (in shares)	1,000			7,000			69,000	38,000