CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 259,798	$ 194,244	$ 147,951
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	0	0	8,976
Other comprehensive (loss) income, net:
Unrealized (loss) gain on AFS securities, net of tax effect of $15,099, $3,922, and $(17,749), respectively	(24,254)	(6,117)	29,683
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	31	90	0
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Subordinated Debt	(2,077)	(4,276)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	(2,077)	(4,276)	0
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(3,500)	(6,523)	1,380
Realized (gain) loss on sale of AFS securities included in income, net of tax effect of $404, $230, and $283, respectively	(655)	(385)	(474)
Net other comprehensive (loss) income	(26,955)	(10,688)	38,185
Comprehensive income	$ 232,843	$ 183,556	$ 186,136