Retirement and Compensation Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Multiemployer Plans [Line Items]
Entity Tax Identification Number	421411715
Multiemployer Plan Number	001
Multiemployer Plan, Period Contributions	$ 30,000	$ 30,000	$ 16,800
Cash-based restricted stock unit plan [Member]
Multiemployer Plans [Line Items]
Tax Benefit from Compensation Expense	$ 1,200	$ 900	600
Class A common stock compensation plans [Member]
Multiemployer Plans [Line Items]
Tax Benefit from Compensation Expense			$ 100