Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Contingency [Line Items]
Current expense (benefit)	$ 27,585	$ (1,399)	$ 58,845	$ 41,725
Deferred (benefit) expense	(5,897)	16,694	6,128	37,318
Total income tax provision	21,688	$ 15,295	$ 64,973	$ 79,043
Reconciliation between the statutory federal income tax rate and the effective income tax rate from continuing operations
Statutory federal income tax rate			35.00%	35.00%
Investment income not subject to federal tax			(3.90%)	(2.70%)
Tax credits			(0.30%)	(7.30%)
State income taxes, net of federal benefit			2.80%	2.50%
Other, net			(0.50%)	(0.40%)
Effective income tax rate			33.10%	27.10%
Reconciliation of unrecognized tax benefits
Increase (decrease) in unrecognized tax benefit			$ 4,694	$ (5,824)
Minimum
Reconciliation of unrecognized tax benefits
Additional increase to unrecognized tax benefits	6,000		6,000
Maximum
Reconciliation of unrecognized tax benefits
Additional increase to unrecognized tax benefits	$ 7,000		$ 7,000