Income Taxes (Rollforward of Valuation Allowances) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 114,964	$ 94,921	$ 70,411
Expenses	14,775	46,385	54,707
Purchase accounting	(15,671)	0	0
Deductions	(7,111)	(12,977)	(3,810)
State income tax, net of Federal impact	536	529	2,998
REIT activity	22,840	(45,781)	(3,583)
Balance at End of Year	121,472	114,964	94,921
Valuation Allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	503,531	352,528	331,458
Purchase accounting	0	172,932	0
Expenses	6,589	21,375	25,199
Deductions	(2,668)	(397)	(2,077)
Other activity (not resulting in expense or deduction)	(808)	2,345	(1,467)
Balance at End of Year	$ 514,349	$ 503,531	$ 352,528