Earnings per Share (EPS) - Reconciliation of Net Income and Weighted Average Common Shares Outstanding (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 123,602	$ 124,536	$ 15,380	$ 149,523	$ 146,958	$ 144,630	$ 136,405	$ 127,720	$ 413,041	$ 555,713	$ 467,363
Basic weighted average shares outstanding (in shares)	111,908	111,908	102,500	97,949	97,830	97,822	97,798	97,595	106,098	97,762	97,403
Dilutive effect of nonvested shares (in shares)									278	465	571
Diluted weighted average shares outstanding (in shares)	112,310	112,134	102,605	98,326	98,376	98,257	98,170	98,104	106,376	98,227	97,974
Basic earnings per share (in dollars per share)	$ 1.10	$ 1.11	$ 0.15	$ 1.53	$ 1.50	$ 1.48	$ 1.39	$ 1.31	$ 3.89	$ 5.68	$ 4.80
Diluted earnings per share (in dollars per share)	$ 1.10	$ 1.11	$ 0.15	$ 1.52	$ 1.49	$ 1.47	$ 1.39	$ 1.30	$ 3.88	$ 5.66	$ 4.77