Parent Company Parent Company Condensed Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Non-interest income	$ 16,027	$ 19,441	$ 14,218	$ 15,410	$ 13,611	$ 4,418	$ 13,444	$ 11,643	$ 65,095	$ 43,116	$ 45,344
Interest expense	43,447	49,186	48,167	43,832	38,455	31,178	27,494	20,477	184,633	117,604	60,849
Non-interest expense	129,699	125,955	114,213	112,914	111,129	113,841	102,548	98,149	482,781	425,667	360,941
Income before income taxes and equity in undistributed earnings of subsidiaries	154,301	155,908	147,686	146,332	139,995	118,615	130,004	121,714	604,226	510,328	451,817
Income tax benefit	(26,236)	(28,533)	(24,750)	(25,536)	(20,909)	(7,492)	(25,325)	(20,814)	(105,055)	(74,540)	(126,325)
Net income	$ 128,065	$ 127,375	$ 122,936	$ 120,796	$ 119,086	$ 111,123	$ 104,679	$ 100,900	499,171	435,788	325,492
Consolidated Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends from subsidiaries									134,000	152,116	97,264
Interest income									2,818	2,905	2,547
Non-interest income									5,112	761	2,470
Total income									141,930	155,782	102,281
Interest expense									14,554	13,949	11,459
Non-interest expense									19,543	19,025	16,293
Total expense									34,097	32,974	27,752
Income before income taxes and equity in undistributed earnings of subsidiaries									107,833	122,808	74,529
Income tax benefit									5,628	10,436	5,229
Income before equity in undistributed earnings of subsidiaries									113,461	133,244	79,758
Equity in undistributed earnings of subsidiaries									385,710	302,544	245,734
Net income									$ 499,171	$ 435,788	$ 325,492