Retirement and Employee Benefit Plans (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Contribution expense	$ 2,500,000	$ 2,200,000	$ 1,900,000
Contributions capitalized	2,900,000	2,800,000	3,800,000
Amount of amortization of prior period service costs reclassified from AOCI to general and administrative expenses	21,000,000
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in accumulated other comprehensive income (loss)	19,200,000	(8,400,000)
Change in accumulated other comprehensive income (loss) after tax	11,600,000	(5,000,000)
Prior service costs	100,000
Net loss	200,000
Company's expected contribution	12,000,000
Net periodic pension cost	13,471,000	11,072,000	9,796,000
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in accumulated other comprehensive income (loss)	1,800,000	(2,400,000)
Change in accumulated other comprehensive income (loss) after tax	1,100,000	(1,400,000)
Company's expected contribution	400,000
Net periodic pension cost	2,871,000	2,401,000	1,695,000
United States Postretirement Benefit Plan of US Entity, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan included in accumulated other comprehensive income (loss)	(15,900,000)	(36,900,000)
Defined benefit plan included in accumulated other comprehensive income (loss) after tax	(9,600,000)	(22,300,000)
Change In Plan Assets [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	12,520,000	11,084,000
Change In Plan Assets [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 115,000	$ 84,000