Shareholders' Equity (Details) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended		5 Months Ended	6 Months Ended		7 Months Ended	12 Months Ended	13 Months Ended
	May 18, 2015 shares	Jan. 31, 2016 USD ($) $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares	Jun. 30, 2015 USD ($) $ / shares	May 31, 2015 $ / shares	Jun. 30, 2016 USD ($) $ / shares shares	Jun. 30, 2015 USD ($) $ / shares shares	Jan. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares
Shareholders' Equity (Details) [Line Items]
Payments of Ordinary Dividends, Common Stock						$ 104,713	$ 124,238
Dividends Payable			$ 17,451	$ 17,560		$ 17,451	$ 17,560			$ 17,451
Reverse Stock Split Ratio of Common Stock	0.50
Common Stock, Shares, Outstanding (in Shares) | shares			174,670,726			174,670,726			174,368,340	174,670,726
Common Stock, Shares, Issued (in Shares) | shares			174,670,726			174,670,726			174,368,340	174,670,726
Distributions [Member]
Shareholders' Equity (Details) [Line Items]
Common Stock, Dividends, Per Share, Cash Paid (in Dollars per share) | $ / shares			$ 0.30	$ 0.3267		$ 0.60	$ 0.6667
Payments of Ordinary Dividends, Common Stock			$ 52,400	$ 60,800		$ 104,700	$ 124,200
Dividends Payable, Amount Per Share (in Dollars per share) | $ / shares			$ 0.10			$ 0.10			$ 0.10	$ 0.10
Dividends Payable			$ 17,500			$ 17,500			$ 17,400	$ 17,500
Annual Distribution [Member]
Shareholders' Equity (Details) [Line Items]
Annual Distribution rate (in Dollars per share) | $ / shares					$ 1.36					$ 1.20
Tender Offer [Member]
Shareholders' Equity (Details) [Line Items]
Stock Repurchase Program, Authorized Amount									$ 200,000
Stock Repurchase Program Commencement Date									May 18, 2015
Stock Repurchase Program Expiration Date									Jun. 22, 2015
Stock Repurchased and Retired During Period, Shares (in Shares) | shares									10,500,000
Stock Repurchased During Period, Price Per Share (in Dollars per share) | $ / shares									$ 19.00
Stock Repurchased and Retired During Period, Value									$ 200,000
Percent of Common Shares Properly Tendered									97.00%
Stock Repurchase, Costs Incurred									$ 600
Share Repurchase Program [Member]
Shareholders' Equity (Details) [Line Items]
Stock Repurchase Program, Authorized Amount		$ 500,000	475,000			$ 475,000		$ 500,000		$ 475,000
Stock Repurchased and Retired During Period, Shares (in Shares) | shares		20,000						1,300,000
Stock Repurchased and Retired During Period, Value		$ 400						$ 22,400
Stock Repurchased During Period, Weighted Average Market Purchase Price Per Share (in Dollars per share) | $ / shares		$ 18.10						$ 17.62
Share Repurchase Program, Extension Description						In June 2016, the Board of Directors approved a one-year extension of the program authorizing share repurchases up to an aggregate of $475 million.
Stock Repurchase Program, Remaining Authorized Repurchase Amount			$ 475,000			$ 475,000				$ 475,000
Share Repurchase Program End Date						July 2017
Terminated Share Redemption Program [Member]
Shareholders' Equity (Details) [Line Items]
Stock Repurchased and Retired During Period, Shares (in Shares) | shares							800,000
Stock Repurchased During Period, Price Per Share (in Dollars per share) | $ / shares							$ 18.40
Stock Repurchased and Retired During Period, Value							$ 14,900
Share Redemption Program, Termination Date							April 2015
Common Shares Prior to Reverse Share Split [Member]
Shareholders' Equity (Details) [Line Items]
Common Stock, Shares, Outstanding (in Shares) | shares	372,200,000
Common Stock, Shares, Issued (in Shares) | shares	372,200,000
Common Shares After Reverse Share Split [Member]
Shareholders' Equity (Details) [Line Items]
Common Stock, Shares, Outstanding (in Shares) | shares	186,100,000
Common Stock, Shares, Issued (in Shares) | shares	186,100,000