Shareholder's Equity (Narrative) (Details) $ / shares in Units, $ in Thousands					1 Months Ended	3 Months Ended				12 Months Ended
	Nov. 25, 2014 USD ($) $ / shares	Aug. 29, 2014 USD ($) $ / shares	Jul. 16, 2014 shares	Jul. 02, 2014 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares	Mar. 31, 2015 USD ($) $ / shares	Dec. 31, 2015 USD ($) installment $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares
Preferred Stock
Preferred stock dividends | $										$ 9,056	$ 4,503	$ 0
Stock Incentive Plans:
Excess tax benefit from share-based compensation | $										$ 4,001	$ 3,177	$ 7,247
Number of shares authorized for grant under share incentive plan					1,200,000	1,200,000				1,200,000
Shares available for future grants/issuance under stock incentive plan					900,039	900,039				900,039
Unrecognized compensation cost on non vested awards | $					$ 16,600	$ 16,600				$ 16,600
Weighted average period										1 year 1 month 12 days
Shares granted, Number of Shares										313,498	272,780	291,863
Shares granted, Weighted Average Grant Price (usd per share) | $ / shares										$ 56.19	$ 43.12	$ 31.66
Stock Repurchased Under Repurchase Program [Member]
Common Stock:
Repurchase of common stock, shares												1,154,378
Repurchase of common stock | $												$ 42,700
Average price per share | $ / shares												$ 36.93
Stock Repurchased To Cover Employee Tax Withholdings [Member]
Common Stock:
Repurchase of common stock, shares										67,000	100,720
Repurchase of common stock | $										$ 3,700	$ 4,600
Stock Options [Member]
Stock Incentive Plans:
Award vesting period										4 years
Options term										10 years
Employees [Member] | Restricted Stock [Member]
Stock Incentive Plans:
Award vesting period										4 years
Number of installments in restricted stock granted. | installment										3
Stock Options [Member]
Stock Incentive Plans:
Number of anti-dilutive options										0	0	0
Common Stock [Member]
Common Stock:
Issuance of stock (in shares)				9,775,000	5,835,000
Issuance of stock, price per share | $ / shares				$ 45.00	$ 80.00
Stock offering expenses | $				$ 18,500	$ 19,100
Mandatory Convertible Preferred Stock [Member]
Common Stock:
Issuance of stock (in shares)				1,725,000
Issuance of stock, price per share | $ / shares				$ 100.00
Stock offering expenses | $				$ 5,900
Preferred Stock
Dividend rate										5.25%
Initial liquidation preference (usd per share) | $ / shares					$ 100	$ 100				$ 100
Consecutive trading day										20 days
Dividends declared (usd per share) | $ / shares	$ 1.3125	$ 1.2979				$ 1.3125	$ 1.3125	$ 1.3125	$ 1.3125
Preferred stock dividends | $	$ 2,300	$ 2,200				$ 2,300	$ 2,300	$ 2,300	$ 2,300
Sheridan Healthcare [Member] | Common Stock [Member]
Common Stock:
Shares of common stock issued for acquisition			5,713,909
Minimum [Member] | Mandatory Convertible Preferred Stock [Member]
Preferred Stock
Conversion rate (shares)					1.8141	1.8141				1.8141
Maximum [Member] | Mandatory Convertible Preferred Stock [Member]
Preferred Stock
Conversion rate (shares)					2.2222	2.2222				2.2222
Restricted Stock Units (RSUs) [Member]
Stock Incentive Plans:
Award vesting period										3 years
Shares granted, Number of Shares										68,533
Shares granted, Weighted Average Grant Price (usd per share) | $ / shares										$ 55.40
Financial performance goal term										1 year
Percent of units granted										150.00%
Restricted Stock Units (RSUs) [Member] | Minimum [Member]
Stock Incentive Plans:
Percent of units granted										0.00%
Restricted Stock Units (RSUs) [Member] | Maximum [Member]
Stock Incentive Plans:
Percent of units granted										150.00%