Income Taxes (Income Tax Benefit (Expense) Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Federal expense at statutory tax rate	$ (64,887)	$ (54,818)	$ (45,942)
Nontaxable income of NNN	63,353	53,178	44,746
State taxes, net of federal benefit	(196)	(200)	(139)
Amortization of built-in gain tax	372	761	613
Expiration of built-in gain tax	1,792	0	0
Other	(58)	(6)	(58)
Valuation allowance (increase) decrease	(619)	0	7,671
Total benefit (expense) for income taxes	$ (243)	$ (1,085)	$ 6,891