Income Taxes (Asset/Liability) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net losses and credit carryforwards	$ 90,773	$ 92,537
Deferred revenue	149,022	132,359
Deferred Tax Assets, Investment in Subsidiaries	14,501	0
Employee benefits	47,823	46,586
Accrued expenses and loss reserves	38,024	32,796
Other	20,693	1,042
Less: valuation allowance	(44,880)	(19,171)
Total deferred tax assets	315,956	286,149
Deferred tax liabilities:
Depreciable and amortizable assets	415,879	279,435
Investment in affiliates	18,624	11,199
Other	0	4,658
Deferred tax liabilities	434,503	295,292
Net deferred tax liabilities	$ (118,547)	$ (9,143)