Income Taxes - Net Operating Losses and Tax Rates (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Net operating losses
State income tax rate (as a percent)	2.60%
Statutory Federal income tax rate (as a percent)	35.00%
Alternative minimum tax credit without expiration	$ 17,589	$ 21,391
Valuation allowance on acquired non-amortizable intangible tax assets and other tax assets	8,877	8,126
Domestic tax authority
Net operating losses
Operating loss carryforward	763,900	189,000
State
Net operating losses
Operating loss carryforward	$ 469,200	$ 352,200