Parent Company Income Statement (Details) - USD ($) $ 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
Expenses
Interest expense		$ 5,362	$ 7,036	$ 8,867	$ 13,076	$ 13,710	$ 15,026	$ 16,125	$ 9,018	$ 34,341	$ 53,879	$ 25,536
Income tax benefit			11,199	7,779	2,148	14,368	17,036	10,007	11,522	31,669	52,933	34,304
Net Income		$ 34,641	$ 34,873	$ 24,902	$ 26,751	$ 47,477	$ 51,845	$ 30,628	$ 35,225	121,167	165,175	121,622
Parent Company [Member]
Income
Dividend Income, Operating	[1]									166,033	181,790	71,255
Total income										166,033	181,790	71,255
Expenses
Interest expense										5,432	8,236	4,234
Total expenses										5,432	8,236	4,234
Income before income taxes and equity in undistributed income of subsidiaries										160,601	173,554	67,021
Income tax benefit										(1,499)	(2,262)	(1,151)
Income of parent company										162,100	175,816	68,172
Equity (deficit) in undistributed income of subsidiaries										(40,933)	(10,641)	53,450
Net Income										$ 121,167	$ 165,175	$ 121,622

[1] Majority of balance eliminates in consolidation.