Fair Value: (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2013 Carrying Value	Dec. 31, 2012 Carrying Value	Dec. 31, 2013 Fair Value	Dec. 31, 2012 Fair Value
Grouping Financial Statement Captions
Long-term debt		$ 6,954,293	$ 5,930,449	$ 7,317,476	$ 7,213,365
Description of Variable Rate Basis	LIBOR
Basis Spread on Variable Rate (as a percent)	1.25%

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

No definition available.

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant