Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Net income	$ 20,098	$ 16,928	$ 36,021	$ 35,278
Other comprehensive income (loss):
Change in unrealized gains on securities	(641)	1,494	1,320	1,903
Less: reclassification adjustment for gains in net income	0	(30)	0	(30)
Decrease in fair value of cash flow hedge	837	(907)	1,107	(907)
Total other comprehensive income (loss)	196	557	2,427	966
Comprehensive income	20,294	17,485	38,448	36,244
Less: comprehensive income attributable to noncontrolling interest	(178)	0	(358)	0
Net Income (Loss) Attributable to Noncontrolling Interest	178	0	358	0
Comprehensive income attributable to common stockholders	$ 20,116	$ 17,485	$ 38,090	$ 36,244