Summary of Significant Accounting Policies - Summarized Combined Financial Data For Equity Method Investments - Income Statement (details) (Western Gas Partners [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Western Gas Partners [Member]
Schedule of Equity Method Investments [Line Items]
Revenues	$ 256,632	$ 199,764	$ 153,131
Operating income	176,370	135,577	90,549
Net income	$ 175,060	$ 134,066	$ 88,521