Income Taxes - Schedule of Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (reduction) in income tax resulting from:
Income tax expense at statutory rate									$ 30,281	$ 26,194	$ 20,440
Tax-exempt income, net									(961)	(945)	(931)
State and local income taxes, net									1,676	1,673	1,414
Bank-owned life insurance, net									(715)	(544)	(462)
Non-deductible expenses									407	263	259
Change in estimated rate for deferred taxes									12,117	302	0
Tax benefits of LIHTC investments, net									(257)	(181)	(179)
Other, net									(379)	(760)	(590)
Effective Income Tax Rate Reconciliation, Tax Credit, Amount									(2,141)	0	0
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount									(1,701)	0	0
Total income tax expense	$ 19,820	$ 7,856	$ 5,545	$ 5,106	$ 7,053	$ 6,316	$ 6,747	$ 5,886	$ 38,327	$ 26,002	$ 19,951