Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Redeemable Noncontrolling Interests [Abstract]
Net unrealized gain (loss) on hedging agreements	$ 379	$ 377
Net unrealized gain on available-for-sale securities	340	328
Accumulated other comprehensive income (loss)	719	705
Shareholders' Equity [Abstract]
Net unrealized gain (loss) on hedging agreements	(2,406)	(2,628)
Net unrealized gain on available-for-sale securities	7,238	6,053
Accumulated other comprehensive income (loss)	4,832	3,425
Noncontrolling Interests [Abstract]
Net unrealized gain (loss) on hedging agreements	(3,428)	(3,488)
Net unrealized loss on available-for-sale securities	2,096	1,775
Accumulated other comprehensive income (loss)	(1,332)	(1,713)
Total Accumulated Other Comprehensive Income [Abstract]
Total unrealized gain (loss) on hedging agreements	(5,455)	(5,739)
Total unrealized gain on available-for-sale securities	9,674	8,156
Total accumulated other comprehensive income (loss)	$ 4,219	$ 2,417