CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income:	$ 312,321,000	$ 400,881,000	$ 359,440,000
Other comprehensive income (loss), net of tax:
Changes in fair value on available-for-sale securities, net of tax	92,829,000	81,658,000	(51,464,000)
Changes in fair value of cash flow hedges, net of tax	52,798,000	(5,179,000)	2,660,000
Amortization of net unrealized gains on securities transferred from available-for-sale to held-to-maturity, net of tax	(5,126,000)	184,000	(73,000)
Gain (loss) on cash flow hedges reclassified from other comprehensive income into net income, net of tax	5,542,000	1,588,000	(657,000)
Net loss (gain) on sale of investment securities reclassified from other comprehensive income into net income, net of tax	(728,000)	(4,388,000)	(1,665,000)
Total other comprehensive income (loss), net of tax	145,315,000	82,639,000	(47,869,000)
Total comprehensive income	$ 457,636,000	$ 483,520,000	$ 311,571,000