CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Unrealized gain (loss), net of taxes (benefits)	$ 13,045,000	$ 8,959,000
Less: reclassificaiton adjustment for net gains realized in net income, net of taxes (benefits)	1,650,000	1,257,000
Changes in market value of derivatives, net of taxes (benefits)	5,928,000	3,392,000
Less: reclassification adjustment for net (gains) losses included in net income, net of taxes (benefits)	$ (5,000)	$ (1,109,000)