Earnings Per Share (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of the components of basic and diluted shares in the EPS Calculation [Abstract]
Weighted-average basic common shares outstanding	175,800,000	175,400,000	176,500,000
Potential number of shares issuable under the Company's LTSIP	300,000	600,000	1,000,000
Weighted-average diluted common shares outstanding	176,100,000	176,000,000	177,500,000
Dividend Reinvestment and Stock Purchase Plan [Abstract]
Shares issued	0	0	0
Shares reserved for future issuance	19,996,038