Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Consolidated Statements Of Comprehensive Income [Abstract]
Net income attributable to common shareholders	$ 63,617	$ 50,659		$ 163,768		$ 130,008
Other comprehensive income, net of tax:
Unrealized holding gain on investments, net of tax of $9 and $73 for the nine months and $32 and $22 for the three months ended, September 30, respectively	60	42		18		139
Reclassification adjustment for loss (gain) reported in net income, net of tax (benefit) of $(49) and $172 for the nine months and $82 for the three months ended, September 30, respectively		(153)	[1]	90	[2]	(319)	[2]
Comprehensive income	$ 63,677	$ 50,548		$ 163,876		$ 129,828

[1] Amount of pre-tax gain of $(235) reclassified from accumulated other comprehensive income to gain on sale of other assets on the consolidated statements of net income for the three months ended September 30, 2012.

[2] Amount of pre-tax loss (gain) of $139 and $(491) reclassified from accumulated other comprehensive income to loss (gain) on sale of other assets on the consolidated statements of net income for the nine months ended September 30, 2013 and 2012, respectively.