Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ 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
Selected Quarterly Financial Information [Abstract]
Interest income	$ 337,757	$ 355,101	$ 346,893	$ 325,561	$ 321,718	$ 301,754	$ 286,852	$ 253,869	$ 1,365,312	$ 1,164,193	$ 879,299
Interest expense	89,372	102,933	103,340	89,947	81,045	69,579	55,140	43,569	385,592	249,333	117,971
Net interest income	248,385	252,168	243,553	235,614	240,673	232,175	231,712	210,300	979,720	914,860	761,328
Provision for credit losses	17,000	11,000	27,000	20,000	35,000	13,000	27,000	12,000	75,000	87,000	44,000
Net interest income after provision for credit losses	231,385	241,168	216,553	215,614	205,673	219,175	204,712	198,300	904,720	827,860	717,328
Non-interest income	17,761	20,301	24,364	30,014	15,280	25,518	17,279	19,947	92,440	78,024	74,256
Non-interest expense	158,690	149,370	141,561	140,378	129,862	136,143	132,131	126,960	589,999	525,096	465,876
Income before income taxes	90,456	112,099	99,356	105,250	91,091	108,550	89,860	91,287	407,161	380,788	325,708
Income tax expense	16,539	23,958	21,387	22,411	19,200	22,998	18,424	19,342	84,295	79,964	128,645
Net income	73,917	88,141	77,969	82,839	71,891	85,552	71,436	71,945	322,866	300,824	197,063
Preferred stock dividends	2,437	2,438	2,437	2,438	2,437	2,438	2,437	2,438	9,750	9,750	9,750
Net income available to common stockholders	$ 71,480	$ 85,703	$ 75,532	$ 80,401	$ 69,454	$ 83,114	$ 68,999	$ 69,507	$ 313,116	$ 291,074	$ 187,313
Basic earnings per share:
Basic earnings per common share	$ 1.42	$ 1.70	$ 1.50	$ 1.60	$ 1.38	$ 1.66	$ 1.39	$ 1.40	$ 6.23	$ 5.83	$ 3.78
Diluted earnings per share:
Diluted earnings per common share	$ 1.42	$ 1.70	$ 1.50	$ 1.60	$ 1.38	$ 1.65	$ 1.38	$ 1.38	$ 6.21	$ 5.79	$ 3.73