Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Comprehensive Income [Abstract]
Net income	$ 107,182	$ 90,898	$ 81,132
Other comprehensive income (loss):
Change in unrealized gains on securities	(234)	1,645	1,750
Less: reclassification adjustment for gains in net income	0	(30)	(9,899)
Decrease in fair value of cash flow hedge	3,563	(1,017)	0
Less: reclassification adjustment for amounts recognized in net income	(1,346)	(224)	0
Total other comprehensive income (loss)	1,983	374	(8,149)
Comprehensive income	109,165	91,272	72,983
Less: comprehensive income attributable to noncontrolling interest	(999)	(167)	0
Comprehensive income attributable to common stockholders	$ 108,166	$ 91,105	$ 72,983