Stockholders' Equity - Reconciliation of Beginning and End of Period Equity Accounts (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule Of Stockholders Equity [Line Items]
Beginning Balance			$ 990,866
Beginning Balance			1,157,625
Balance at December 31, 2013			166,759
Reclassification of redeemable noncontrolling shareholder interest			(152,250)
Net income	47,699	(168)	131,315	91,398
Net income			133,950
Other comprehensive income			9,276
Other comprehensive income	810	13,114	8,288	34,311
Accelerated stock repurchase program			(200,000)
Dividends payable to noncontrolling shareholders			(2,570)	(9,790)
Stock compensation plans, including tax benefit of $234			8,724
Ending Balance	168,435		168,435
Balance at September 30, 2014	41,793		41,793
Cash dividends - $.315 per share			(19,432)
Ending Balance	893,530		893,530
Ending Balance	935,323		935,323
Redeemable Noncontrolling Shareholder Interest [Member]
Schedule Of Stockholders Equity [Line Items]
Reclassification of redeemable noncontrolling shareholder interest			152,250
Net income			17,173
Other comprehensive income			(988)
Ending Balance	168,435		168,435
Noncontrolling Shareholder Interest in Consolidated Subsidiary [Member]
Schedule Of Stockholders Equity [Line Items]
Balance at December 31, 2013			166,759
Reclassification of redeemable noncontrolling shareholder interest			(123,965)
Net income			2,635
Other comprehensive income			(1,066)
Dividends payable to noncontrolling shareholders			(2,570)
Balance at September 30, 2014	41,793		41,793
Total Parent Stockholders' Equity [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance			990,866
Reclassification of redeemable noncontrolling shareholder interest			(28,285)
Net income			131,315
Other comprehensive income			10,342
Accelerated stock repurchase program			(200,000)
Stock compensation plans, including tax benefit of $234			8,724
Cash dividends-$.315 per share			(19,432)
Ending Balance	$ 893,530		$ 893,530