Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Consolidated Statements Of Comprehensive Income [Abstract]
Net income attributable to common shareholders	$ 67,996		$ 63,617		$ 166,424		$ 163,768
Other comprehensive income, net of tax:
Unrealized holding (loss) gain on investments, net of tax (benefit) expense of $(33) and $32 for the three months and $73 and $9 for the nine months ended, September 30, respectively	(62)		60		136		18
Reclassification adjustment for loss reported in net income, net of tax benefit of $134 and $49 for the nine months ended, September 30, respectively		[1]		[1]	249	[1]	90	[1]
Comprehensive income	$ 67,934		$ 63,677		$ 166,809		$ 163,876

[1] Amount of pre-tax loss of $383 and $139 reclassified from accumulated other comprehensive income to loss on sale of other assets on the consolidated statements of net income for the nine months ended September 30, 2014 and 2013, respectively.