Income Taxes - Provision, Reconciliation and UTB (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current	$ 84,445	$ 32,031	$ 76,842
Deferred	(167,059)	53,481	21,682
Total income tax provision	$ (82,614)	$ 85,512	$ 98,524
Reconciliation between the statutory federal income tax rate and the effective federal income tax rate from continuing operations
Statutory federal income tax rate	35.00%	35.00%	35.00%
Federal tax rate change resulting from tax reform	(61.40%)	0.00%	0.00%
Investment income not subject to federal tax	(4.30%)	(3.00%)	(3.00%)
Tax credits	(0.30%)	(6.90%)	(0.20%)
State income taxes, net of federal benefit	2.30%	2.30%	3.20%
Other, net	(0.10%)	(0.40%)	(0.90%)
Effective federal income tax rate	(28.80%)	27.00%	34.10%
Reconciliation of unrecognized tax benefits
Balance, beginning of year	$ 17,268	$ 23,093	$ 26,890
Additions to tax positions in the current year	13,461	0	1,383
Additions to tax positions in the prior year	0	1,902	50
Reductions to tax positions from statutes expiring	0	(7,727)	(5,230)
Balance, end of year	$ 30,729	$ 17,268	$ 23,093