Subsequent Events (Details Textual)				3 Months Ended								12 Months Ended
	Jan. 25, 2021 $ / ft²	Jan. 11, 2021 USD ($)	Jan. 28, 2019	Dec. 31, 2020 USD ($) $ / shares	Sep. 30, 2020 USD ($) $ / shares	Jun. 30, 2020 USD ($) $ / shares	Mar. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Sep. 30, 2019 USD ($) $ / shares	Jun. 30, 2019 USD ($) $ / shares	Mar. 31, 2019 USD ($) $ / shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Subsequent Event [Line Items]
Stock dividend rate, percentage			8.00%
Net Income				$ 147,488,000	$ 98,938,000	$ 84,396,000	$ 36,760,000	$ 92,589,000	$ 50,580,000	$ 54,593,000	$ 40,550,000	$ 367,582,000	$ 238,312,000	$ 210,780,000
Less: distributed earnings allocated to participating securities												(583,000)	(466,000)	(413,000)
Less: undistributed earnings allocated to participating securities												(1,748,000)	(1,020,000)	(846,000)
Net income attributable to common stockholders (numerator for basic earnings per share)												365,251,000	236,826,000	209,521,000
Add back: undistributed earnings allocated to participating securities												1,748,000	1,020,000	846,000
Less: undistributed earnings reallocated to participating securities												$ (1,704,000)	$ (992,000)	$ (833,000)
Basic (in shares) | shares												63,455,422	61,616,988	60,571,123
Diluted (in shares) | shares												65,441,279	63,702,666	61,830,761
Basic ( in dollars per share) | $ / shares				$ 2.27	$ 1.54	$ 1.33	$ 0.58	$ 1.48	$ 0.81	$ 0.88	$ 0.66	$ 5.76	$ 3.84	$ 3.46
Diluted (in dollars per share) | $ / shares				$ 2.19	$ 1.49	$ 1.31	$ 0.56	$ 1.42	$ 0.79	$ 0.86	$ 0.64	$ 5.58	$ 3.72	$ 3.39
Pro Forma
Subsequent Event [Line Items]
Net Income												$ 367,582,000	$ 238,312,000	$ 210,780,000
Less: distributed earnings allocated to participating securities												(583,000)	(466,000)	(413,000)
Less: undistributed earnings allocated to participating securities												(1,748,000)	(1,020,000)	(846,000)
Net income attributable to common stockholders (numerator for basic earnings per share)												365,251,000	236,826,000	209,521,000
Add back: undistributed earnings allocated to participating securities												1,748,000	1,020,000	846,000
Less: undistributed earnings reallocated to participating securities												(1,704,000)	(992,000)	(833,000)
Numerator For Earnings Per Share Diluted Under Two Class method												$ 365,295,000	$ 236,854,000	$ 209,534,000
Basic (in shares) | shares												68,531,856	66,546,347	65,416,813
Diluted (in shares) | shares												70,676,581	68,798,880	66,777,222
Basic ( in dollars per share) | $ / shares												$ 5.33	$ 3.56	$ 3.20
Diluted (in dollars per share) | $ / shares												$ 5.17	$ 3.44	$ 3.14
Share-based Payment Arrangement, Option
Subsequent Event [Line Items]
Add: dilutive effect of stock options and performance share units (in shares) | shares												1,659,265	1,737,945	984,076
Share-based Payment Arrangement, Option | Pro Forma
Subsequent Event [Line Items]
Add: dilutive effect of stock options and performance share units (in shares) | shares												1,792,006	1,876,981	1,062,802
Performance Shares
Subsequent Event [Line Items]
Add: dilutive effect of stock options and performance share units (in shares) | shares												326,592	347,733	275,562
Performance Shares | Pro Forma
Subsequent Event [Line Items]
Add: dilutive effect of stock options and performance share units (in shares) | shares												352,719	375,552	297,607
Subsequent Event
Subsequent Event [Line Items]
Stock dividend rate, percentage	8.00%
Stock, dividend rate, per shares owned, number | $ / ft²	12.5
Subsequent Event | Senior Notes Due January 2030
Subsequent Event [Line Items]
Face amount		$ 350,000,000
Stated interest rate		2.50%
Par price, percentage		100.00%
Proceeds from debt, net of issuance costs		$ 347,700,000
Unamortized discount, total		$ 2,300,000