Employee Benefit Plans - Postretirement Healthcare Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure
Amortization of gain, weighted average remaining service period (in years)	4 years
Total stockholders’ equity	$ 2,013,900	$ 1,693,900		$ 982,600
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Defined Benefit Plan, Amortization of Transition Asset (Obligation)	$ 700
Postretirement Healthcare Plan
Defined Benefit Plan Disclosure
Minimum age requirement	55 years
Requisite service period	15 years
Accumulated other comprehensive income (loss), before tax, related to the Plan	$ 500
Reduction in accumulated post-retirement benefit obligation due to curtailment				2,800
Reduction in net periodic benefit cost due to curtailment			$ (300)	$ (2,800)
Unfunded benefit obligation	(400)	(500)
Net periodic benefit cost	700	$ 800	$ 400
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
2019	90
2020	60
2021	50
2022	40
2023 through 2027	80
Estimated amount amortized from accumulated other comprehensive loss into net periodic benefit costs	$ 120
Minimum
Defined Benefit Plan Disclosure
Assumptions used calculating net periodic benefit cost, discount rate	3.60%	3.60%
Maximum [Member]
Defined Benefit Plan Disclosure
Assumptions used calculating net periodic benefit cost, discount rate	5.50%	6.00%