Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended			24 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Income Taxes (Textual) [Abstract]
Net tax benefit due to the tax effects of the 2017 Act				$ 15,600
Operating loss carryforwards	$ 7,000			7,000
Valuation allowance	4,900			4,900
Net deferred tax asset related to tax credit carryforwards	67,500			67,500
Valuation allowance	4,930	$ 25,489		4,930
Consolidated income (loss) subject to tax	158,600	(55,600)	$ 109,300
Cash paid for income taxes	11,522	7,401	$ 2,152
Low-Income Housing and Rehabilitation Tax Credit Carryforward
Income Taxes (Textual) [Abstract]
Valuation allowance	$ 15,400	$ 15,400		$ 15,400
Minimum
Income Taxes (Textual) [Abstract]
Expiration years of net operating loss carryforwards	Dec. 31, 2019
Tax credit carryforward, expiration date	Dec. 31, 2034
Maximum
Income Taxes (Textual) [Abstract]
Expiration years of net operating loss carryforwards	Dec. 31, 2034
Tax credit carryforward, expiration date	Dec. 31, 2038