Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 14, 2014
Class of Stock [Line Items]
Common Stock, Shares, Issued during a Period			26,700,000	85,600,000
Preferred Stock, Shares Outstanding	0	0	0
Common Stock, Shares, Issued	220,082,610	220,255,502	220,082,610
Proceeds from Issuance of Common Stock			$ 321,900	$ 826,200
Preferred Stock, Par or Stated Value Per Share	$ 1	$ 1	$ 1		$ 1.00
Preferred Stock, Redemption Price Per Share					$ 25.00
Preferred Stock, Redemption Amount					$ 94,800
Preferred Share Original Issuance Costs	$ (3,500)	$ 0	$ 3,530	$ 2,656
Percentage of Restrictions on Ownership of Company Common and Preferred Stock			3.90%
Document Fiscal Year Focus		2015	2014	2013