Earnings Per Share (Details) (USD $)	0 Months Ended	3 Months Ended
	Feb. 18, 2014	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income (loss)		$ 97,595,000	$ 87,016,000
Stock Issued During Period, Shares, New Issues	9,200,000
Shares Issued At Overallotment Option	1,200,000
Share Price	$ 44.00
Net proceeds from equity offering	390,200,000
Basic Earnings per Share from Continuing Operations
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic		216,000	232,000
Income from continuing operations available to common shareholders		97,379,000	86,784,000
Basic weighted average shares outstanding		101,581,000	91,841,000
Net income per share - Basic		$ 0.96	$ 0.95
Diluted Earnings per Share from Continuing Operations
Income from continuing operations available to common shareholders		97,379,000	86,784,000
Effect of dilutive stock options and other shares		0	0
Income from continuing operations available to common shareholders		97,379,000	86,784,000
Basic weighted average shares outstanding		101,581,000	91,841,000
Additional dilutive stock options and other shares		0	2,000
Diluted weighted average shares outstanding		101,581,000	91,843,000
Net income per share - Diluted		$ 0.96	$ 0.95
Earnings Per Share Diluted Other Disclosures Abstract
Anti-dilutive stock options excluded from computation of diluted earnings per share (in shares)		0	0
Share Repurchase Program - Shares Purchased		0	0
Authorized Commercial Paper		$ 1,250,000,000
Summary of Stock Option Activity [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number		0