Income Tax - Income Tax Expense Differs from Computed Income Tax at Statutory Rates (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Computed income tax at statutory rates			$ 17,602	$ 22,563
Benefit of net tax-exempt interest income			(15)	(36)
Differences in tax rates due to multiple jurisdictions			1,149	3
Tax benefit due to a change in estimate			131	300
Effect of income subject to tax-exemption grant			(12,050)	(16,322)
Unrecognized tax expense			193	202
Other expense (benefit)			2,028	(412)
Income tax expense	$ 4,520	$ 2,489	$ 9,038	$ 6,298