Cash Equivalents and Investments (Summary of Cash and Available-For-Sale Securities) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Sep. 30, 2014		Dec. 31, 2013		Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-For-Sale Securities [Line Items]
Adjusted Cost	$ 285,107		$ 97,802
Unrealized Gains	0		1,738
Unrealized Losses	(653)		0
Cash, Cash Equivalents and Available-for-Sale Securities, Fair Value	284,454		99,540
Cash and Cash Equivalents	281,607	[1]	94,302	[2]	319,596	131,212
Short-Term Marketable Securities	2,847	[1]	5,238	[2]
Cash [Member]
Schedule of Available-For-Sale Securities [Line Items]
Adjusted Cost	108,267		8,332
Unrealized Gains	0		0
Unrealized Losses	0		0
Cash, Cash Equivalents and Available-for-Sale Securities, Fair Value	108,267		8,332
Cash and Cash Equivalents	108,267		8,332
Short-Term Marketable Securities	0		0
Money Market Funds [Member]
Schedule of Available-For-Sale Securities [Line Items]
Adjusted Cost	173,340		85,970
Unrealized Gains	0		0
Unrealized Losses	0		0
Cash, Cash Equivalents and Available-for-Sale Securities, Fair Value	173,340		85,970
Cash and Cash Equivalents	173,340		85,970
Short-Term Marketable Securities	0		0
Equity Securities [Member]
Schedule of Available-For-Sale Securities [Line Items]
Adjusted Cost	3,500		3,500
Unrealized Gains	0		1,738
Unrealized Losses	(653)		0
Cash, Cash Equivalents and Available-for-Sale Securities, Fair Value	2,847		5,238
Cash and Cash Equivalents	0		0
Short-Term Marketable Securities	$ 2,847		$ 5,238

[1] unaudited

[2] Note 1