Parent Company Information - Schedule of Condensed Statements of Cash Flows (Detail) - 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
Cash flows from operating activities:
Net Income	$ 38,104	$ 81,891	$ 76,468	$ 113,330	$ 77,102	$ 69,559	$ 72,802	$ 41,965	$ 309,793	$ 261,428	$ 161,907
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation									14,726	19,472	12,204
Net amortization of premiums and accretion of discounts on borrowings									29,512	38,454	46,346
Losses on securities transactions, net									150	2,342	20
Losses on sales of assets, net	(1,336)	$ 159	$ 564	(77,720)	280	$ 1,899	$ 125	97	(78,333)	2,401	95
Net change in:
Other assets									(163,330)	(33,145)	(57,353)
Net cash provided by operating activities									1,463,950	593,589	619,230
Cash flows from investing activities:
Sales of investment securities available for sale									271,901	44,377	2,727
Cash and cash equivalents acquired in acquisitions									22,239	156,612	0
Net cash used in investing activities									(2,131,341)	(3,129,551)	(1,547,548)
Cash flows from financing activities:
Proceeds from issuance of preferred stock, net									0	0	98,101
Dividends paid to preferred shareholders									(12,688)	(15,859)	(6,277)
Dividends paid to common shareholders									(146,537)	(138,857)	(115,881)
Purchase of common shares to treasury									(1,805)	(3,801)	(2,645)
Common stock issued, net									2,957	2,704	8,207
Net cash provided by financing activities									673,449	2,548,481	951,927
Net change in cash and cash equivalents									6,058	12,519	23,609
Cash and cash equivalents at beginning of year				428,629				416,110	428,629	416,110	392,501
Cash and cash equivalents at end of year	434,687				428,629				434,687	428,629	416,110
Parent Company
Cash flows from operating activities:
Net Income									309,793	261,428	161,907
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of subsidiary									(197,714)	(113,705)	(44,664)
Stock-based compensation									14,726	19,472	12,204
Net amortization of premiums and accretion of discounts on borrowings									124	63	197
Losses on securities transactions, net									0	(3)	0
Losses on sales of assets, net									0	147	0
Net change in:
Other assets									19,768	9,928	(89)
Accrued expenses and other liabilities									8,803	(10,657)	8,737
Net cash provided by operating activities									155,500	166,673	138,292
Cash flows from investing activities:
Sales of investment securities available for sale									0	257	0
Cash and cash equivalents acquired in acquisitions									11,947	7,915	0
Capital contributions to subsidiary									0	0	(98,000)
Net cash used in investing activities									11,947	8,172	(98,000)
Cash flows from financing activities:
Proceeds from issuance of preferred stock, net									0	0	98,101
Dividends paid to preferred shareholders									(12,688)	(15,859)	(6,277)
Dividends paid to common shareholders									(146,537)	(138,857)	(115,881)
Purchase of common shares to treasury									(1,805)	(3,801)	(2,644)
Common stock issued, net									2,957	2,704	8,207
Net cash provided by financing activities									(158,073)	(155,813)	(18,494)
Net change in cash and cash equivalents									9,374	19,032	21,798
Cash and cash equivalents at beginning of year				$ 109,839				$ 90,807	109,839	90,807	69,009
Cash and cash equivalents at end of year	$ 119,213				$ 109,839				$ 119,213	$ 109,839	$ 90,807