Summary of Significant Accounting Policies (Reconciliation of Net Income to Taxable Income Before Dividends Paid Deduction) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Net income (loss)	$ 246,455	$ 196,549	$ (75,868)
Book/tax differences	2,675	50,127	148,462
Taxable income before adjustments	249,130	246,676	72,594
Less: capital gains	(98,267)	(109,133)	0
Adjusted taxable income subject to 90% distribution requirement	$ 150,863	$ 137,543	$ 72,594