Investments (Tables)

3 Months Ended

Mar. 31, 2013

Investments

Schedule of fair value of held-to-maturity securities recorded at amortized cost

	March 31, 2013		December 31, 2012
	($ in thousands)
U.S. Treasury securities	$	393,258	$	483,775
Corporate securities		1,217,076		510,691
Commercial paper		650,506		562,975
Certificates of deposit		25,000		7,000
Total	$	2,285,840	$	1,564,441

Schedule of held-to-maturity securities included in the entity's condensed consolidated balance sheets

	March 31, 2013		December 31, 2012
	($ in thousands)
Cash and cash equivalents	$	92,556	$	254,732
Short-term investments		1,287,298		789,668
Short-term restricted funds		90,449		90,440
Long-term restricted funds		302,783		393,334
Long-term investments		512,754		36,267
	$	2,285,840	$	1,564,441

Schedule of contractual maturities of held-to-maturity securities

	March 31, 2013				December 31, 2012
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
	($ in thousands)
Within 1 year	$	1,773,086	$	1,773,086	$	1,528,174	$	1,528,174
After 1 year		512,754		512,754		36,267		36,267
	$	2,285,840	$	2,285,840	$	1,564,441	$	1,564,441