Income Taxes - Reconciliation of Income Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Amount
Tax provision (benefit) at United States statutory rates on consolidated income or loss subject to tax	$ 33,296	$ (19,459)	$ 38,257
State income tax expense, net of federal tax (benefit) expense	12,252	(1,769)	7,152
Establishment of deferred tax asset related to partnership basis difference	0	(3,501)	0
Effect of permanent differences	302	(1,629)	(132)
Tax effect of intercompany transactions	(33,250)	0	(47,369)
Tax credits	(6,897)	(9,607)	(16,750)
Tax reform revaluation	288	(15,894)	0
Increase in valuation allowance	(20,434)	21,023	0
Other	1,416	0	0
Total income tax benefit	$ (13,027)	$ (30,836)	$ (18,842)
Percent
Tax provision (benefit) at United States statutory rates on consolidated income or loss subject to tax	21.00%	35.00%	35.00%
State income tax expense, net of federal tax (benefit) expense	7.70%	3.20%	6.50%
Establishment of deferred tax asset related to partnership basis difference	0.00%	6.30%	0.00%
Effect of permanent differences	0.20%	2.90%	(0.10%)
Tax effect of intercompany transactions	(21.00%)	(0.00%)	(43.30%)
Tax credits	(4.40%)	17.30%	(15.30%)
Tax reform revaluation	0.002	0.286	0.000
Increase in valuation allowance	(12.90%)	(37.80%)	0.00%
Other	0.90%	0.00%	0.00%
Total income tax benefit	(8.30%)	55.50%	(17.20%)
Tax Credit Carryforward [Line Items]
Valuation allowance against the deferred tax assets associated with rehabilitation tax credits due to lower federal tax rate under the 2017 Act	$ 4,930	$ 25,489
Low-Income Housing and Rehabilitation Tax Credit Carryforward
Tax Credit Carryforward [Line Items]
Valuation allowance against the deferred tax assets associated with rehabilitation tax credits due to lower federal tax rate under the 2017 Act	$ 15,400	$ 15,400