Investments in Unconsolidated Entities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Equity method investments, combined income statements
Revenues	$ 1,620,402	$ 1,471,192
Operating expenses	1,137,209	1,034,624
Operating income	483,193	436,568
Other income, net	1,764	598
Net income	$ 484,957	$ 437,166