Construction Reserve Funds (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Construction Reserve Funds [Abstract]
Penalty tax rate	1.10%
Construction reserve fund	$ 252,100,000	$ 186,000,000
Withdrawals	65,493,000	122,695,000	82,553,000
Deposits	131,603,000	58,350,000	18,642,000
Construction reserve fund benefit	$ 66,110,000	$ (64,345,000)	$ (63,911,000)